LIBRARY
OF TIIK
UNIVERSITY OF CALIFORNIA;
^T OK*
Mrs. SARAH P. WALSWORTH.
Received October, 1894. Accessions No . 5j? ~ Class No.
BBIT13H
ARTS & SCIENCES
PHILADELPHIA.
Planter.
AMERICAN EDITION
OF THE
BRITISH ENCYCLOPEDIA,
OR
DICTIONARY
OF
ARTS AND SCIENCES,
COMPRISING
AN ACCURATE AND POPULAR VIEW
OF THE PRESENT
IMPROVED STATE OF HUMAN KNOWLEDGE.
BY WILLIAM NICHOLSON,
Author and Proprietor of the Philosophical Journal, and various other Chemical, Philosophical, and Mathematical Works.
ILLUSTRATED WITH
UPWARDS OF 180 ELEGANT ENGRAVINGS, VOL. V.
PHILADELPHIA :
PUBLISHED BY MITCHELL, AMES, AND WHITE,
ALSO,
BY INGRAM AND LLOYD, NASHVILLE.
William Brown, Printer,
1819.
v.5"
OT TBS
toiri; 7]
•SJFO-
THE
BRITISH ENCYCLOPEDIA,
ELLIPSIS.
ELLIPSIS, in geometry, a curve line returning into itself, and produced from the section of a cone by a plane cut- ting- both its sides, but not parallel to the base. See CONIC SECTIONS.
The easiest way of describing this curve, in piano, when the transverse and conjugate axis A B, E D, (Plate V. MiscelK fig. 1.) are given, is this: first take the points F, /, in the transverse axis A B, so that the distances C F, C/, from the centre C, be each equal to v/ A C— C D ; or that the lines F D,/D, be each equal to A C : then, having fixed two pins ;n the points F,,/J which are culled the foci of the ellipsis, take a thread equal in length to the transverse axis A B; and fastening its two ends, one to the pin F, and the other to/, with another pin M stretch the thread tight ; then if this pin M be moved round till it returns to the place from whence it first s'et out, keeping 'the thread always ex- ter.aed so as to form the triangle F M/, it will describe an ellipsis, whose axes are A B, D E
The greater axis, A B, passing through the two foci F/, is called the transverse axis ; and the lesser one D E, is called the conjugate, or second axis : these two always bisect each other at right angles, and the centre of the ellipsis is the point C, where they intersect. Any right line passing through the centre, and terminat- ed by the curve of the ellipsis on each side, is called a diameter ; and two dia- meters, which naturally bisect all the parallels to each other, bounded by the
ellipsis, are called conjugate diameters, Any right line, not passing through the centre, but terminated by the ellipsis, and bisected by a diameter, is called the ordinate, or ordinate-applicate, to that diameter; and a third proportional to two conjugate diameters is called the latus rectum, or parameter of that diameter, which is the first of the three propor- tionals.
The reason of the name is this : let B A, E D, he any two conjugate diame- ters of an ellipsis (fig. 2, where they are the two axes) at the end A, of the dia- meter A B, raise the perpendicular A F, equal to the latus rectum, or parameter, being a third proportional to A B, E D, and draw the right line B F ; then, if any point P betaken in B A, and an ordinate P M be drawn, cutting B F in N, the rectangle under the absciss A P, and the line P N will be equal to the square of the ordinate P M. Hence drawing N O pa- rallel to A B, it appears that this rec- tangle, or the square of the ordinate, is less than that under the absciss A P, and the parameter A F, by the rectan- gle under A P and O F," or N O and OF; on account of which deficiency, Appollonius first gave this curve the name of an ellipsis, from eAA5/9re*v, to be deficient.
In every ellipsis, as A E B D, (fig. 2), the squares of the semi-ordinates M P, m p. are as the rectangles under the seg- ments of the transverse axis A P X P B, Ap X p B, made b) these ordinates re- spectively ; which holds equally true of
ELL
the circle, where the squares of the ordi- nates are equal to such rectangles, as be- ing mean proportionals between the seg- ments of the diameter. In the same man- ner, the ordinates to any diameter what- ever are as the rectangles under the seg- ments of that diameter.
As to the other principal properties of the ellipsis, they may be reduced to the following propositions. 1. If from any point M in an ellipsis, two right lines, M F, M/, (fig. 1,) be drawn to the foci F, /, the sum of these two lines will be equal to the transverse axis A B. This is evi- dent from the manner of describing an ellipsis. 2. The square of half the lesser axis is equal to the rectangle under the segments of the greater axis, contained between the foci and its verticles ; that is, DC1 = AF XFB = A/'x/B. 3. Every diameter is bisected in the centre C. 4. The transverse axis is the great- est, and the conjugate axis the least, of all diameters. 5. Two diameters, one of which is parallal to the tangent in the vertex of the other, are conjugate diame- ters ; and, vice versa, a right line drawn through the vertex of any diameter, pa- rallel to its conjugate diameter, touches the ellipsis in that vertex. 6. If four tan- gents be drawn through the vertices of two conjugate diameters, the parallelo- gram contained under them will be equal to the parallelogram contained under tangents drawn through the vertices of any other two conjugate diameters. 7. If aright line, touching an ellipsis, meet two conjugate diameters produced, the rectangle under the segments of the tan- gent, between the point of contact and these diameters, will be equal to the square of the semi-diameter, which is conjugate to that passing through the point of contact. 8. In every ellipsis, the sum of the squares of any two conjugate diameters is equal to the sum of the squares of the two axes. 9. In every ellipsis, the angles F GI, /G H, (fig. 1), made by the tangent II I, and the lines FG, /G, drawn from the foci to the point of contact, are equal to each other. 10. The area of an ellipsis is to the area of a circumscribed circle, as the lesser axis is to the greater, and vice versa with respect to an inscribed circle ; so that it is a mean proportional between two cir- cles, having the transverse and conjugate axes for their diameters. This holds equally true of all the other correspond- ing- parts belonging to an ellipsis.
The curve of any ellipsis may be obtain- ed by tj*e following series. Suppose the
ELL
semi-transverse axis C B = r, the semi- conjugate axis C D=c.andthe semi-ordi- nate = a; then the length of the curve
TU r> , r* a3 4 r1 c1 tf— r a* M o = a H -4-
40 c8
8 c4 r* gi -\- r6 a"i — 4 c1 . _
n2~c^ — — , &c. And
if the species of the ellipsis be determin- ed, this series will be more simple : for if
+ 2048r*
2r, then M B =
113a7 3419 a?
458752^ +75497472r8,
- Thls
series will serve for an hyperbola, by making the even parts of all the terms affirmative, and the third, fifth, seventh, &c. terms negative.
The periphery of an ellipsis, according to Mr. Simpson, is to that of a circle, whose diameter is equal to the transverse axis
?<.* ir • d $dt
of the ellipsis, as 1-— _____
3. 3 . 5</3 2 . 3 . 5 . 5 . 7 d+
2.2.4.4.6.6~~ 2 .2 .4.4 .6.6. 8.8 8cc. is to 1 , where d is equal to the differ- ence of the squares of the axis applied to the square of the transverse axis.
ELLIPSIS, in grammar, a figure of syn- tax, wherein one or1 more words are not expressed ; and from this deficiency it has got the name ellipsis.
ELLIPSIS, in rhetoric, a figure nearly allied to preterition, when the orator, through transport of passion, passes over many things, which, had he been cool, ought to have been mentioned. In prete- rition, the omission is designed ; which, in the ellipsis, is owing to the vehemence of the speaker's passion, and his tongue not being able to keep pace with 'the emotion of his mind.
ELLIPTIC, or ELLIPTICAL, some- thing belonging to an ellipsis. Thus we meet with elliptical compasses, elliptic conoid, elliptic space, elliptic stairs, &c. The elliptic space is the area contained within the curve of the ellipsis, which is to that of a circle described on the transverse axis, as the conjugate dia- meter is to the transverse axis ; or it is a mean proportional between two circles, described on the conjugate and trans- verse axis.
ELLIPTO1DES, in geometry, a name used by some to denote infinite ellipses,
m-\-n
defined by the equation ag =bxm n.
ELO
ELY
Of these there are several sorts : thus, if a yi = b -rj (a — x) it is a cubical elip- toid ; and if a y* = b x- (a — jr)1, it de- notes a biquadratic elliptoid, which is an ellipsis of the third order in respect of the appollonian ellipsis.
ELL1SIA, in botany, so called in me- mory of John Ellis, F. R. S. a genus of the Pentandria Monogynia class and or- der. Natural order of Luridse. Borra-. gineae, Jussieu. Essential character : co- rolla funnel-form, narrow? berry dry, two-celled, two valved ; seeds two, dot- ted, one placed over the other. There is only one species, viz. E. nyctelea, cut- leaved ellisia, a native of Virginia.
ELM. See ULMUS. The elm is very serviceable in places where it may lie con- tinually dry or wet in extremes. Ac- cordingly, it is proper for water-works, mills, the ladles and soles of the wheel- pipes, pumps, aqueducts, pales, and ship- planks beneath the water-lines. It is also ©fuse for wheel-rights, handles for sin- gle saws, axle-trees, and the like. The clearness of the grain makes it also fit for all kinds of carved works, and most ornaments relating to architecture.
ELOCUTION, in rhetoric, the adapt- ing words and sentences to the things or sentiments to be expressed. It consists of elegance, composition, and dignity. The first, comprehending the purity and perspicuity of language, is the founda- tion of elocution. The second ranges the words in proper order ; and the last adds the ornaments of tropes and figures, to give strength and dignity to the whole.
ELOGY, a praise or panegyric bestow- ed on any person or thing, in considera- tion of its merit. The beauty of elogy consists in an expressive brevity. Elogi- ums should not have so much as one epi- thet, properly so called, nor two words sy- nonirnous. They should strictly adhere to truth ; for extravagant and improbable elogies rather lessen the character of the person or thing they would extol.
ELONGATION, in astronomy, the di- gression or recess of a planet from the sun, with respect to an eye placed on our earth. The term is chiefly used in speak- ing of Venus and Mercury, the arch of a great circle intercepted between either of these planets and the Sun being called the elongation of that planet from the Sun.
But here it is to be observed, that it is only a circle which has the sun for its centre; that the greatest elongation is in a line touching the planet's orbit. For in an elliptic orbit it may be, that tke
elongation from the sun may grow still greater, even after it has left the place where the line joining the earth and planet touches the orbit. For after that, the true distance of the planet from the Sun may increase, whilst the distance ef the Sun and planet from the earth does not increase, but rather decrease. But because the orbits of the planets are near- ly circular, such small differences may be neglected in astronomy. The greatest elongation of Venus is found by observa- tion to be about forty-eight degrees, and the greatest elongation of Mercury about twenty-eight degrees, upon which a<S- count this planet is rarely to be seen with the naked eye.
ELONGATIOK, angle of, is an angle contained under lines drawn from the centre of the sun and planet to the centre of the earth.
ELOPEMENT, is when a married wo- man of her own accord departs from her husband, and dwells with an adulterer; for which, without voluntary reconcilia- tion to the husband, she shall lose her dower by the statute cf Westminster, 2. c. 34. Except that her husband will- ingly, and without coercion of the church, reconcile her, and suffer her to dwell with him, in which case, she shall be re- stored to her action, 13 Ed. I. st. 1. c. 34. By eloping in this manner, or living in adultery apart from the husband, he is discharged of her future debts, and no longer liable to support her.
ELOQUENCE, the art of speaking well, so as to affect and persuade. Cicero de- fines it the art of speaking with copious- ness and embellishment. Eloquence and rhetoric differ from each other, as the theory from the practice ; rhetoric being the art which describes the rules of elo- quence, and eloquence that art which uses them to advantage. See RHETO- RIC.
ELOPS, in natural history, a genus of fishes of the order Abdominales. Gene- ric character : head smooth, edges of the jaws and palate rough, with teeth ; gill membrane with thirty rays, and armed on the outside in the middle with five teeth. The saury elops, the only species, bears a considerable resemblance to a salmon, from which it differs principally in want- ing the fleshy back fin. It inhabits the shores of Carolina and the West Indies; in Jamaica it passes by the name of the sun-fish. It is in general about fourteen inches long.
ELYMUS, in botany, lymcgrass, a ge- mts of the Triandria Digynia cla'ss and
EMB
EMB
©rder. Natural order of Gramina, or Grasses. Essent al character : calyx late- ral, two-valved, aggregate, many flower- ed. The American species are 10 in number, riz. 1. E. arenarius. 2. E. phi- ladelphicus. 3. E. canadensis. 4. E. vir- ginicus 5. E. striatus. 6. E. europaeus, 7. E. villosus. 8. E. hystric. 9. E. cilia- tus. 10. E. glaucifolius. (Muhl.)
EMARGINATED, among botanists, an appellation given to such leaves as have a liUle indenting on their summits : when tliis indenting is terminated on each side by obtuse points, they are said to be ob- tusely emargmated ; whereas, when these points are acute, they are culled acutely emarginated.
EMBALMING, is the opening a dead body, taking out the intestines, and filling the place with odoriferous and desicca- tive drugs and spices, to prevent its pu- trefying. The Egyptians excelled all other nations in the art of preserving bo- dies from corruption ; for some that they have embalmed upwards of 2000 years ago remain whole to this day, and are often brought into other countries as great curiosities. Their manner of em- balming was thus ; they scooped the brains with an iron scoop out at the nos- trils, and threw in medicaments to fill up the vacuum : they also took out the en- trails, ami having filled the body with myrrh, cassia, and other spices, except frankincense, proper to dry up the hu- mours, they pickled it in nitre, where it lay soaking for seventy days. The body was then wrapped up in bandages of fine linen and gums, to make it stick like glue ; and so was delivered to the kin- dred of the deceased, entire in all its features, the very hairs of the eye-lids be- ing preserved. They used to keep the bodies of their ancestors, thus embalmed, in little houses magnificently adorned, and took great pleasure in beholding them alive, as it were, without any change in their size, features, or complexion. The Egyptians also embalmed birds, &c. The prices for embalming were different ; the highest was a talent, the next 20 minae, and so decreasing to a very small mat- ter ; but those who had not wherewithall to answer this expense, contented them- selves with infusing, by means of a syringe, through the fundament, a cer- tain liquor extracted from the cedar, and, leaving it there, wrapped up the ')0(\y in salt of nitre : the oil thus preyed upon the intestines, so that, when they took it out, the intestines came away vvith it, dried, and not in the least putre-
fied : the body, being inclosed in grew dry, und nothing reirviiiitd besides the skin giueU upon tht nones. .
The ir.ethoci ot embalm, ;ȣ used by the modern Egyptians, according :. Maillet, is, to vvasii the body several times rose-watev, which, he elsewhere observes, is more fragrant in that country than With us, They afterwards perfume it \v.tL m cense, aloes, anil a quantity of otiier odours, of which they are by no rntans sparing1; and then they bury the body in a winding-sheet, made partly 01 bilk aiid partly ot cotton, and moistened, as is sup- posed, witn some sweet scented water or liquid perfume, though Aiaillet uses only the term moistened; this they cover with, another cloth of unmixed cotton, to which they add one ot the richest su.ts of clothes of the deceased. The expense, he says, on these occasions, is very great, though nothing like what the genuine em- balming cost in former times.
EMBARGO, in commerce, an arrest on ships, or merchandize, by public au- thority ; or a prohibition of state, com- monly on foreign ships, in time of war, to prevent their going out of port ; some- times to prevent their coming in ; and sometimes both, for a limited time. The king may lay embargoes on ships, or em- ploy those of his subjects, in time of danger, for service and defence of the na- tion ; but they must not be for the private advantage of a particular trader, or com- pany : and, therefore, a warrant to stay a single ship is no legal embargo. No in- ference can be made from embargoes which are only in war time, and are a prohibition by advice of council, and not a prosecution of parties. If goods be laden on board, and after an embargo or restraint from the prince or state comes forth, and then the master of the ship breaks ground, or endeavours to sail, if any damage accrues, he must be respon- sible for the same : the reason is, because his freight is due, and must be paid, nay though the goods be seized as contra- band. Embargo differs from quarantine, insomuch as this last is always for the term of forty days, in which persons from foreign parts infected with the plague are not permitted to come on shore. See QUARANTINE .
EMBASSADOR, or AMBASSADOR a public minister sent from one sovereign prince, as a representative of his person, to another.
Embassadors are either ordinary or ex- traordinary. Embassador in ordinary is he who constantly resides in the court of
EMB
EMB
another prince, to maintain a good under- standing1, and look to the interest of his tnaster Till about two hundred years ago, •embassadors in ordinary were not heard of; all, till then, were embassadors extra- ordinary; that is, such as are sent on some particular occasion, and who retire as soon as the affair is dispatched.
By the law of nations, none under the quality of a sovereign prince can send or receive an embassador. At Athens, em- bassadors mounted the pulpit of the pub- lic orators, and there opened their com- mission, acquainting the people with their errand. At Rome, they were introduced to the Senate, and delivered their com- missions to them.
Embassadors should never attend any public solemnities, as marriages, funerals, &c. unless their masters have some inter- " est therein: nor must they go into mourn- ing on any occasions of their own, because they represent the persons of their prince. By the civil law, the moveable goods of an embassador, which are ac- counted an accession to his person, can- not be seized OR, neither as a pledge, nor for payment of a debt, nor by order or execution of judgment, nor by the King's or state's leave where he resides, as some conceive; for all actions ought to be far from an embassador, as well that which toucheth his necessaries, as his person: if, therefore, he hath contracted any debt, .he is to be called upon kindly, and if he refuses, then letters of request are to go to his master. Nor can any of the embas- sador's domestic servants, that are regis- tered in the Secretaries of State's Office, be arrested in person or goods: if they are, the process shall be void, and the parties suing out and executing it shall suffer and be liable to such penalties and corporal punishment, as the Lord Chan- cellor, or either of the chief justices, shall think fit to inflict. Yet embassadors cannot be defended when they commit any thing against that state, or the per- son of the prince, with whom they re- side; and if they are guilty of treason, felony, &c. or any other crime against the law of nations, they lose the privilege of an embassador, and may be subject to punishment as private aliens.
EMBER -weeks, or days, in the Christian Church, are certain seasons of the year, set apart for the imploring God's blessing, by prayer and fasting, upon the ordina- tions performed in the church at such times. These ordination fasts are ob- served four times in the year, viz. the Wednesday, Friday, and Saturday, af-
ter the first Sunday in Lent, after Whit- sunday, after the fourteenth of Septem- ber, and the thirteenth of December ; it being enjoined, by a canon of the church, that deacons and ministers be ordained, or made, only upon the Sundays immedt- ately following these ember fusts. The ember-weeks were formerly observed in different churches with some variety, but were at last settled as they are now ob- serve-d, by the council of Placentia, anno 1095 The council of Mentz, convened by Charlemagne, mentions the ember- weeks as a new establishment.
EMBERIZA, the buntir.g, in natural history, a genus of birds of the order Passeres. Generic character: bill conic; mandibles receding from each other, from the base downwards ; the lower with the sides narrowed in ; the upper containing a large knob, of use to break hard seeds. There are, according to Gmelin, seventy-seven species. Latham enumerates sixty-three, of which the most important are the following: E. ni- valis, the snow bunting. These birds are about the size of a chaffinch, and have been found in the most northern latitudes to which navigators have pene- trated. They are found, not merely on the land about Spitzbergen, but upon the ice contiguous to it, though merely graminivorous birds, of which genus they are the sole species found in that cli- mate. In the north of Great Britian they sometimes appear in vast flocks, and are considered as the harbingers of a severe winter. They are known in Scotland by the name of snow flake. E. hortulana, the ortolan, is somewhat less than the yellow-hammer, is common in France and Italy, in Germany and Sweden. These birds are migratory, and in their pass- age are caught in vast multitudes, to be fed for the table, being considered as extremely delicate and luxurious food. They are enclosed by professional feed- ers in dark rooms, where oats, and other grains, and seeds, are provided for tlv m in the fullest abundance. On these arti- cles they feed with such voracity, that in a short time they attain that size, which it is impossible for them to ex- ceed, and constitute, it may almost be said, one mass of exquisitely flavoured and luscious fat. From this state they would soon sink in lethargy, but they are now killed by their owners for the market. A full-fed ortolan weighs about three ounces. It rarely passes farther north than Russia, and is not to be found in. England, or the United States. By
EMB
EMB
many its notes are particularly admired. It sometimes builds on low hedges, and occasionally on the ground, and generally breeds twice a year. E. citrinella, or the yellow hammer, is extremely common in Great Britain, where it lays its eggs on the ground, or in some low bush, con- structing it with little art ; it possesses no interesting musical tones, and is tame and stupid in its character ; it feeds on grain and in.sects, and is to be found in almost every country in Europe; its flesh in England is generally bitter, but in Italy the yellow hammer is fattened like the ortolan for the table, and is in considerable estimation. E. miliaria, the common bunt- ing. These birds are also particularly common in England, and appear fre- quently in vast flocks, especially in the winter, during which they are caught in nets, or shot in vast numbers, and sold to many under the successful pretence of their being a species of larks. They are stationary in England, but on the con- tinent are birds of passage. During the incubation of the female, the male is ob- served frequently on the bare and promi- nent branch of some neighbouring tree, exerting himself vo cheer her confinement by his song, which, however, is harsh and monotonous in the extreme ; at short in- tervals he utters a sort of trembling shriek, several times repeated. E. or zi- Tora,or the rice bird, is peculiar to Ame- rica, where its depredations on the rice and maize subject it to the peculiar aver- sion of the farmer. They are occasion- ally kept for the sake of their music. They frequent the shores of rivers in the eastern and northern states, during the autumn, in immense flocks, feeding on the seeds of wild rice, or reeds, as they are called in Pennsylvania (Zizania clavu- losa). They are then shot in great num- bers for the market, are extremely fat and delicious, not inferior to the ortolan. During the season of their loves, the co- lour of the male differs very considerably from that of the female, but gradually as- similates with it, until, in the autumn, they are almost undistinguishable from each other by colour. Their brumal re- treat is unknown. It is, however, far to the south, and perhaps without the boun- daries of the United States. For the cirl bunting, see Aves, Plate VI. fig. 4. For the black-head bunting, see Aves, Plate VT. fig. 5.
EMBEZZLEMENT, in law, by stat. 39 Geo. 3. c. 35. for protecting masters against embezzlement by their clerks and servants : servants or clerks, or per-
sons employed for the purpose, or in the capacity of servants or clerks, who shall, by virtue of such employment, receive, or take into their possession, any money, goods, bond, bill, note, banker's draft, or other valuable security or effects, for or in the name, or on the account of, their mas- ter or employer ; or who shall fraudently embezzlCj secrete, or make away with the same, or any part thereof; every such offender shall be deemed to have feloniously stolen the same from his mas- ter or employer, for whose use, or on whose account, the same was delivered to or taken into the possession of such ser- vant, clerk, or other person so employed, although such money, goods, bond, bill, note, banker's draft, or other valuable security, was or were no otherwise re- ceived into the possession of his or their servants, clerk, or other person so em- ployed; and every such offender, his adviser, procurer, aider, or abetter, being thereof lawfully convicted or attainted, shall be liable to be transported beyond seas.
EMBLEM, a kind of painted enigma, or certain figures painted or cut meta- phorically, expressing some action, with reflections underneath, which, in some measure, explain the sense of the device, and at the same time instruct us in some moral truth, or other matter of know- ledge. The emblem is somewhat plain- er than the enigma, and the invention is more modern, it being entirely unknown to the ancients.
EMBLEMENTS, in law, signify the profits of land sown ; but the word is sometimes used more largely, for any profits that arise and grow naturally from the ground, as grass, fruit, hemp, flax, &c.
EMBOL1SMIC, or intercalary, a term used by chronologists in speaking of the additional months and years which they insert, to bring the lunar to the solar year. Since the common lunar year consists of twelve synodic months, or 354 days near- ly, and the solar consists of 365 days (throwing away the odd hours and mi- nutes; it is plain that the solar year will exceed the lunar by about 11 days; and, consequently, in the space of about 33 years, the beginning of the lunar year will be carried through " all the seasons, and hence it is called the moveable lunar year. This form of the year is used at this time by the Turks and Arabians; and because in three year's time the so- lar year exceeds the lunar by 33 days, therefore, to keep the lunar months in
EMB
EMB
the same seasons and times of the solar year, or near it, chronologists added a •whole month to the lunar year every third year, and so made it consist of 13 months ; this year they called the ernbo- lismic year, and the additional month the embolismic. or emholimeun, or interca- lary month This form of the year is called the fixed lunar year, and it was used by the Greeks and Romans till the time of Julius Caesar.
EMBOSSING, or IMBOSSIXG, in archi- tecture and sculpture, the forming or fashioning works in relievo, whether cut with a chizzel or otherwise. Embossing is a kind of sculpture, wherein the fi- gures stick out from the plane whereon it is cut ; and according as the figures are more or less prominent, they are said to be in alto, mezzo, or basso relievo ; or high, mean, or low relief.
EMBOTHRIUM, in botany, a genus of the Tetrandria Monogynia class and or- der. Natural order of Protex, Jussieu. Essential character: corolla four-petalled; anthers sessile, sitting on the tips of the petals ; follicle round. There are four species.
EMBRACERY, is an attempt to cor- rupt or influence a jury, or any way in- cline them to be more favourable to the one side than the other, by money, pro- mises, letters, threats, or persuasions, whether the juror, on whom such attempt is made, give verdict or not, or whether the verdict given be true or false, which is punished by fine and imprisonment ; and the juror taking money, perpetual infamy, imprisonment for a year, and for- feiture of tenfold the value.
EMBRASURE, in fortification, a hole or aperture in a parapet, through which the cannon are pointed, to fire into the moat or field. Embrasures are generally twelve feet distant from one another, eve- ry one of them being from six to seven feet wide without, and about three within ; their height above the platform is three feet on that side towards the town, and a foot and a half on the other side towards the field ; so that the muzzle may be sunk on occasion, and the piece brought to shoot lowr.
EMBROCATION, in surgery, an ex- ternal kind of remedy, which consists in an irrigation of the part affected with some proper liquor, as oils, spirits, &c. by means of a woollen or linen cloth, or a sponge, dipped in the same. The use of embrocation is either to attenuate and dislodge something obstructed uncler- VOL. V.
neath the skin, to ease pains, or to irri- tate the part into more warmth and a quicker sense of feeling. The pumping used in natural baths is properly an em- brocation.
EMBROIDERY, a work in gold, or stf- ver, or silk thread, wrought by the needle upon cloth, stuff, or muslin, into various figures. In embroidering stuff's, the work is performed in a kind of loom, be- cause the more the piece is stretched, the easier it is worked As to muslin, they spread it upon a pattern ready designed ; and sometimes, before it is stretch" :d up- on the pattern, it is starched, to make it more easy to handle. Embroidery on the loom is less tedious than the other, in which, while they work flowers, all the threads of the muslin, both lengthwise and breadthwise, must be continually counted ; but, on the other hand, this last ism"ch richer in points, and susceptible of greater variety. Cloths too much mill- ed are scarce susceptible of this orna- ment, and in effect we seldom see them embroidered. The thinnest muslins are left for this purpose, and they are em- broidered to the greatest perfection in Saxony ; in other parts of Europe, how- ever, they embroider very prettily, and especially in France.
There are several kinds of embroidery ; as, 1. Embroidery on the stamp, where the figures are raised and rounded, hav- ing cotton or parchment put under them, to support them. 2. Low embroidery, where the gold and silver lie low upon the sketch, and are stiched with silk of the same colour. 3. Guimped embroidery : this is performed either in gold or silver : they first make a sketch upon the cloth, then put on cut vellum, and afterwards sew on the gold and silver with silk thread ; in this kind of embroidery they often put gold and silver cord, tinsel, and spangles. 4. Embroidery on both sides ; that which appears on both skies of the stuff. 5. Plain embroidery, where the fi- gures are flat and even, without cords, spangles, or other ornaments.
ExHKoiDEnr, no foreign embroidery, on gold or silver brocade, is permitted to be imported into this kingdom, on pa n of being seized and burned, and a penalty of 1007. for each piece .
EMBRYO, in physiology, the first ru- diments of an animal in the womb, before the several members are distinctly form- ed ; after which period it is denominat- ed a foetus. See FOETUS and MIJDWWE-
EME
EMK
&-*innro, in botany. See
EMERALD. This mineral comes chief- lyfrom Peru; some specimens have been brought from Egypt Dolomieu found it in the granite of Elba. Hitherto it has been found only crystallized. The primi- tive form of its crystals is are gular six-sided prism ; and the form of its integrant mole- cules is a triangular prism, whose sides are squares, and bases equilateral tri- angles. The most common variety of its crystals is the regular six-sided prism, sometimes with the edges of the prism, or of the bases, or the solid angles, or both, wanting, and small faces in their place.
Crystals short ; lateral planes smooth, terminal planes rough ; colour emerald green, of all intensities ; internal lustre between 3 and 4 ; vitreous ; fracture small, imperfect, conchoidal, with a con- cealed foliated fracture, and fourfold cleavage; fragments sharp-edged; tran- sparency 4 to 2 ; causesdouble refraction ; scratches quartz with difficulty. Specific gravity from 2.600 to 2.7755.
The fossil here described is the occi- dental emerald, and appears from agtique gems to have been known in the earlier ages, though at present it comes to us on- ly from South America. Vauquelin found it to contain of silex64.5, argil 16, glucine 13, oxide of chrome 3.25, lime 1.6, and water 2. The oriental emerald iaa green corundum, of resplendent lustre, supe- rior in hardness to every stone but the diamond, and of the specific gravity of 4.
EMERSION, in astronomy, is when any planet that is eclipsed begins to emerge or get out of the shadow of the eclipsing body. It is also used when a star, before hidden by the sun as being too near him, begins to re-appear or emerge out of his rays.
EMERSON (WILLIAM), in biography, a late eminent mathematician, was born in June, 1701, at Hurworth, a village about three miles south of Darlington, on the borders of the county of Durham ; at least it is certain that he resided here from his childhood. His father, Dudley Emer- son, taught a school, and was tolerably proficient in mathematics ; and without his books and instructions, perhaps., his son's genius, though eminently fitted for mathematical studies, might never have been unfolded. Beside his father's instructions, our author was as- sisted in the learned languages by a young clergyman, then curate of Hur- worth, who was boarded at his father's hxmse. In the early part of his life he at-
tempted to teach a few scholars; but whether from his concise method, for he was not happy in explaining his ideas, or the warmth of his natural temper, he made no progress in his school ; he there- fore soon left it oJF, and, satisfied with a moderate competence left him by his pa- rents, he devoted himself to a studious retirement, which he thus closely pursu- ed, in the same place, through the course of a long life, being mostly very healthy till towards the latter part of his days,, when he was much afflicted with the stone. About the close of the year 1781, being sensible of his approaching dissolu- tion, he disposed of his whole mathemati- cal library to a bookseller at York ; and on May the20th, 1782, his lingering and pain- ful disorder put an end to his life, athis na- tive village, beingnearly 81 years of age,
Mr. Emerson, in his person, was rather short, but strong and well made, with an open countenance and ruddy complexion* being of a healthy and hardy disposition ; he was very singular in his behaviour, dress, and conversation ; his manner and appearance were that of a rude and rather boorish countryman ; he was of very plain conversation, and seemingly rude, com- monly mixing oaths in his sentences, though without any ill intention ; he had strong good natural mental parts, and could discourse sensibly on any subject, but was always positive and impatient of contradiction ; he spent his whole life in close study, and writing books, from the profits of which he redeemed his little patrimony from some original incum- brance ; in his dress he was as singular as in every thing else ; he possessed commonly but one suit of clothes at a time, and those very old in their appear- ance ; he seldom used a waistcoat ; and his coat he wore open before, except the lower button ; and his shirt quite the re- verse of one in common use, the hind side turned foremost, to cover his breast, and buttoned close at the collar behind ; he wore a kind of rusty coloured wig, with- out a crooked hair in it, which probably had never been tortured with a comb from the time of its being made : a hat he would make to last him the best part of a lifetime, gradually lessening the flaps, bit by bit, as it lost its elasticity and hung down, till little or nothing but the crown remained.
He often walked up to London when he had any book to be published, revising sheet by sheet himself : trusting no eye but his own, was always a favourite max- im with him. In mechanical subjects, he.
EMfc
BMP
-always tried the propositions practically, making all the different parts himself on a small scale ; so that his house was tilled with all kinds of mechanical instruments, together or disjointed. He would fre- quently stand up to his middle in water while fishing, a diversion lie was remark- ably fond of. He used to study incessant- ly for some time, and then for relaxation take a ramble to any pot ale house, where he could get any body to drink with, and talk to. The late Mr. Montague was very kind to Mr. Emerson, and ofien visited him, being pleased with his con- versation, and used frequently to come to him in the fields where he was work- ing, and accompany him home, but could never persuade h,m to get into a car- riage ; on these occasions he would some- times exclaim, *' Damn your whim- wham! 1 had rather walk." He was a married man, and his wife used to spin on an old fashioned wheel of his own making, a drawing of which is given in his *• Mechanics."
Mr. Emerson, from his strong, vigorous mind, and close application, had acquired deep knowledge of all the branches of mathematics and physics, upon all parts of which lie wrote good treatises, though in a rough and unpolished stile and man- ner. He was not remarkable, however, for genius, or discoveries of his own, as his works hardly show any traces of ori- ginal invention. He was well skilled in the science of music, the theory of sounds, and the various scales both an- cient and modern ; but he was a very poor performer, though he could make and repair some instruments, and some- times went about the country tuning harpsichords.
The following is the list of Mr. Emer- son's works, all of them printed in bvo., excepting his " Mechanics" and his tk In- crements," in 4to. and his " Navigation" in 12mo. 1. The Doctrine of Fiuxions.
2. The Projection of the Sphere, Ortho- graphic, Stereographic, and Gnomonical.
3. The Elements of Trigonometry. 4. The Principles of Mechanics. 5. A Treatise of Navigation on the Sea. 6. A Treatise on Arithmetic. 7. A Treatise on Geom- etry. 8. A Treatise of Algebra in two books. 9. The Method of Increments.
10. Arithmetic of Infinities, and the Conic Sections, with other Curve Lines.
11. Elements of Optics and Perspective. V2. Astronomy. 13. Mechanics, with Centripetal and Centrifugal Forces. 14. Mechanical Principles of Geography, Navigation, and Dialling. 15. Commen-
tary on the Principia, with the Defence of Newton. 16. Tracts. 17. Miscella- nies.
EMERY, a stone of the ruby family, of which three kinds are usually distinguish- ed in commerce ; the Spanish, red, and common emery. The first sort is found in the gold mines of Peru, and, be;ng judged a kind of rnarcasite of that rich metai, is prohibited to be exported. The red emery is found in copper mines, and the little there is of i in England comes from Sweden and Denmark. The com- mon emery is taken out of iron m.nes, and almost the only sort used in Eng- land ; it is of a brownish colour, border- ing a little on red, exceedingly hard, and in consequence difficult to pulverize. The English are the only people who have the art oi reducing common emery into powder, and thus send it to their neighbours. Of the powder, the most subtile and impalpable is the best : as to the stone, it should be chosen of a high colour, and as free ot the rock as possible.
The consumption of emery is very con- siderable among the armourers, cutlers, lock-smiths, lapidaries, masons, and otuer mechanics; some of whom use it to po- lish and burnish iron and steel works ; others to cut and scollop glass, marble, and precious stones.
EMETIC, a medicine which induces vomiting.
EMETIC tartar, the old name for tar- trite of antimony.
EMOLLIENTS. See PHARMACY.
EMPETRUM, in botany, heath, a ge- nus ot the Dioecia Triandria class and order. Natural order of Ericae, Jussieu. Essential character : male, calyx three- parted; corolla three-petalled; stamens long ; female, calyx three-parted; coroila three-petalled ; styles nine ; berry nine- seeded. There are two species, viz. E. album, white-berried heath, and .E. ni- grum, black-berried heath, crow or crake berry. These are low shrubs, seldom propagated in gardens, unless tor varie- ty's sake. They are natives of wild mountains, where the soil is heathy and full of bogs.
EMPIS, in natural history, a genus of insects of the order Diptera. Generic character: mouth with an inflected si, ck- er and proboscis ; sucker with a s;ngie- vaived sheath and three bristles ; feelers short, filiform; antennae setaceous. These minute insects live by sucking out the blood and juices of other animals There are about thirty species. One of the
ot
ENA
ENA
most common species in Europe is the E. livida, which is a brownish fly ; the wi?igs are transparent, with dark veins. They are obst rved in fields and gardens. E. borealis is of a more slender form than the common window fly, and of a blackish colour, with large, broad, oval wings, of a brown colour, and rurous legs varied with black.
EMPLASTRUM, in pharmacy, a com- position for external use, generally spread upon leather, linen, or some other con- venient thing, before it is applied. See PHARMACY. The following is a re- cipe for makihg the Ladies Court Plas- ter : " Dissolve five ounces of isinglass in a pint of water, and having ready a quantity of thin black sarsenet, stretched in a proper frame, apply the solution warm with a brush equally over the sur- face. This is to be rep -ated, after it is dry, two or three times." Some give it a coat of gum benzoin dissolved in al- cohol ; but this is injurious rather than beneficial.
EMI LEURUM, in botany, a genus of the Monoecia Tetrandna class and or- der. Natural order of Aggregate. Ru- tacese, Jussieu. Essential character : male, calyx four-cleft ; corolla none : fe- male, calyx four-cleft, inferior ; corolla none ; stigma cylindric, placed on the lateral toothlet of the germ ; capsule opening on the side ; seed one, anlled. There is but one species ; viz. E. ser- rulatum, Cape empleurum. This is a shrub, with wand-like, even branches ; leaves like those of a willow, alter- nate, subpetioled, linear-lanceolate, even above, beneath longitudinally wrinkled ; peduncles few-flowered, lateral, much shorter than the leaves ; flowers small, most of them male ; capsules usually so- litary, incurved with a beak of the same length.
EMULSION, a milky looking fluid, caused by an imperfect combination of oil with water, by means of mucilage, gluten, &.c. All oily farinaceous seeds, as nuts, almonds, linseed, &c. form an emulsion by tnturation with water ; yolk of egg, which is a natural compound of oil ana albumen, makes a similar emul- sion.
ENAMELLING. Neri on glass, with the notes of Merret and Kunckel, afford a variety of good receipts for making enamels, though much still remains to be done in this art. The art is indeed retarded by the considerable advantages the enameller derives from the discovery
of any colour uncommonly brilliant;, clear, or hard. On this account the artist na- turally endeavours to keep his process a secret, as the source of private gain. The principal ingredients of enamel co- lours are, however, weil known.
There are two kinds of enamel ; the opaque and the transparent. Transparent enamels are usually rendered opaque by adding putty, or the white oxide of tin, to them. The basis of all enamels is therefore a perfectly transparent and fusible glass. The oxide of tin renders this a oeautiful white, the perfection of which is greater when a small quantity of manganese is likewise added. If the oxide of tin be not sufficient to destroy the transparency ot the mixture, it pro- duces a semi-opaque glass, resembling tiie opal.
Yellow enamel is formed by the addi- tion oi oxide of lead or antimony. Kunc- kel likewise affirms that a beautiful yel- low may be obtained from silver.
Red enamel is formed by the oxide of gold, and also by that of iron. The for- mer is the most beautiful, and stands the fire, which the latter does not.
Oxide of copper affords a green, man- ganese a violet, cobalt a blue, and iron a very fine black. A mixture of these ena- mels produces a great variety of inter- mediate colours, according to their na- ture and proportion. In this branch of the art the coloured enamels are some- times mixed with each other, and some- times the oxides are mixed before they are added to the vitreous bases.
The enamelier who is provided with a set of good colours is very far from being in a situation to practise the art, unless he be skilled in the methods of applying them, and the nature of the grounds up- on which they are to be laid. Many of the metals are too fusible to be enamel- led, and most of them are corroded by the action of the fused glass. For this reason none of the metals are used but goid, silver, and copper. Platina has in- deed been used ; but of its effects and habitudes with enamel very little can be said, for want of a sufficient number of experiments.
The purest gold, of 24 carats, is calcu- lated to produce the best effect with ena- mel. 1. Because it entirely preserves the metallic brilliancy, without undergo- ing any oxidation in the fire. 2. Being less fusible, it will admit of a more re- fractory, and consequently a harder and more beautiful enamel. It is not usual.
ENAMELLING.
however, to enamel on finer gold than 22 carats; and the operation would be very defective, if a coarser kind than that of Ib carats were used. For in this case more alkali must be added to the enamel, to renuer it more fusible, and this addi- tion would, at the same time, render it softer and less brilliant.
Rejecting ail these exceptions, the fol- lowing description may be taken, by way of example, of fixing a transparent blue enamel upon gold ot 22 carats.
The artist begins his operation by breaking his enamel into small .pieces in a steel mortar, and afterwards pulverizing it in a mortar of agate. He is careful to add water in this part of the process, wliidi prevents the splinters of glass from flying about. There are no means of ex- plaining the point at which the tntura- tion ought to be given up, as this can be learned only by experience. Some ena- meis require to be very finely triturated; but others may be used in the form of a coarse powder. As soon as he ap- prehends that his enamel is sufficiently pounded, he washes it by agitation in very clear water, and pouring off the fluid as it becomes turbid. 1 his process, which is made for carrying off dust and every other impurity from the enamel, is con- tinued until the water comes oft as clear as it was poured on.
The workman puts his enamel thus prepared into a white earthern or china saucer, with water poured on it to the depth of about one tenth of an inch. He afterwards takes up the enamel with an iron spatula as equally as posible. As the enamel here spoken of is trans- parent, it is usual to ornament the gold with rose work, or other kinds of work, calculated to produce a good effect through the enamel.
The thickness of this first layer de- pends entirely upon its colour : delicate colours n general require that it should have no great thickness.
The moist enamel, being thus placed, is dried, by applying a very clean half- worn linen cloth to it, which must be very carefully done, to avoid removing the enamel by the action of wip>ng.
In this state the piece is ready for the fire. If it be enamelled on both sides, it is placed upon a tile, or iron plate, hol- lowed out in such a manner, that the un- covered edges of the piece alone are in contact with the support But if it be enamelled on one side only, it is simply laid upon the plate, or upon a tile. Two things, however, require to be attended
to. 1. If the work be very small, or not capable of being enamelled on the oppo- site side, the iron plate must be perfect- ly flat, in order that the work may not bend when softened by heat. 2. If the work be of considerable size, it is always counter-enamelled, if possible ; that is to say, an enamel is applied on the back surface, in order to counteract the ef- fect which the other coating of glass might produce on the soft metal, when it came to contract by cooling.
The enameller's furnace is square, and built of bricks, bedded in an earth pro- per for the purpose. It may be consi- dered as consisting of two parts, the lower part which receives a muffle rest- ing on the floor of the furnace, and open on both sides.
The upper part of the furnace consists of a fire-place, rather larger and longer than the dimensions of the muffle. The fire-place contains the muffle, and must surround it on all sides, except at the bottom. The charcoal is put in at a door above the muffle, which is closed as soon as the fire is lighted. A chim- ney proceeds from the summit of the furnace, with a moderate aperture, which may be closed at the pleasure of the ar- tist, by applying a cast iron plate to it. This furnace differs from that of the as- sayer, in the circumstance that it is sup- plied with air through the muffle itself: for if the draught were beneath the muffle, the heat would be too strong, and could not be stopped when requisite.
As soon as the fire is lighted, and the muffle has acquired the requisite degree of ignition, tiie charcoal is disposed to- wards the lower part of the muffle, in such a manner as that it shall not fall upon the work, which is then conveyed into the muffle, with the greatest care, upon the plate of iron or earthen-ware, which is taken out by long spring pin- cers. The work is placed as near as possible at the farther extremity of the muffle ; and as soon as the artist per- ceives a commencement of fusion, he turns it round with great delicacy, in or- der that the fusion may be very uniform. And as soon as he perceives that the fu- sion has entirely taken place, he instant- ly removes it out of the furnace : for the fusion of gold happens so very near to that of the enamel, that the neglect of a few seconds might be attended with considerable loss.
When the work is cooled, a seond coat of enamel is applied in the same manner as the first, if necessary. This, and the
ENAMELLING.
same cautious management of the fire, are to he repeated for every additional coat of enamel the nature of the work may demand.
As soon as the number of coatings are sufficient, it becomes necessary to give an even surface to the enamel, which, though polished by the fire, is neverthe- less irregular. This is done with a fine grained Lancashire tile and water. As the file wears smooth, sand is used. Much precaution and address are requir- ed in this part of the work, not only be- cause it is easy to make the enamel se- parate in splinters t'rom the metal, but likewise because *he colour would not be uniform, if it were to be ground •thinner at one part than at another.
The deep scratches of the file are in the next place taken out by rubbing the surface wiih a piece of deal wood and fine sand and water. A polish is then given by a second ignition. This polish, however, is frequently insufficient, and not as perfectly uniform as the delica- cy of the work may require.
The substance used by the enamellers as a polishing material is known by the name of rotten-stone, which is prepared by pounding, washing", decanting ott the turbid water, suffering the tine suspend- ed particles to subside from this water, and lastly levigating it upon a glass plate.
The work is then cemented to a square piece of wood, with a mixture of resin and brickdust, and by this means fixed in a vice.
The first operation of polishing is made by rubbing the work with rotten- stone upon a small straight bar of pew- ter. Some delicacy is here required, to avoid scratching or producing flaws in the enamel by pressing too hard. In this way the piece is rendered perfectly even. But the last brilliant polish i,s given by a piece of deal wood and the same rotten-stone.
This is the general method of applying «namel ; but some colours require more precaution in the management of the fire. Opaque colours require less man- agement than the transparent. A variety of circumstances must be attended to in transparent colours ; every colour re- quires gold of a particular fineness.
When different colours are intended to be placed beside one another, they are kept separate by a small edge or prominency, which is left in the gold for that purpose, and is polished along with the enamel.
The enamelling upon silver is effected
nearly in the same manner as that of gold; but the changes tusiaineU by the colours upon silver by tne «cuun of the fire are much more considerable than when gold is used.
Copper is not much used by enamel- lers, on account of the difficulty which attends the attempt to fix beautiful co- lours upon it. When this metal is used, the common practice is, to apply a coat- ing of opaque white enamel, and upon this other colours which are more fusi- ble than the white.
A good effect is produced in toys by leaving part of the gold bare. For this purpose its surface is cut into suitable compartments by the engraver. This, however, is an expensive method, and is for this reason occasionally imitated, by applying small and very thin pieces of gold upon the surface of the enamel, where they are fixed by the fire, and af- terwards covered by a transparent vi- treous coating.
A method of taking off the enamel from any toy, without injuring the metal- lic part, is often a desirable object. For tliis purpose a mixture of common salt, nitre, and alum in powder, is applied upon the enamel, and the piece is put into the furnace. As soon as the fusion has taken place, the piece is to be sud- denly thrown into water, which causes the enamel to fly oft' either totally or in part. Any part which may still remain is to be removed by repeating the same operation a second time.
To coat vessels of iron or copper for culinary purposes with an enamel capa- ble of defending the metal from the ac- tion of any solvent, and for enduring any heat, or transition from heat to cold, ap- pears a desirable object ; and many ex- periments have been made on the sub- ject by Mr. Soen Rinman of the Royal Academy of Stockhlom.
The following compositions he found answer very well on copper. 1. The white semi-transparent fluorspar and sul- phate of lime, in equal quantities, pow- dered, mixed, and calcinated in a white heat ; then powdered, made into a thin paste with water, and applied a little warm to the vessel, also warmed. Then dried and heated gradually to a certain point, a very strong heat, greater than is generally obtained in an assaying fur- nace, is to be applied as quickly as pos- sible. 2. Sixty parts of lime, one hun- dred of flnor spar, sixty of gypsum, twenty of quartz, and one of manga- nese, are calcinated, ground, and applied
ENAMELLING.
in a similar manner. 3. Four parts of fluorspar, four of gypsum, and one of li- tharge, melted into a straw-coloured glass, ground and applied in the same •way, required a much stronger heat. 4. Five parts of fluor spar, five of gyp- sum, two of minium, two of flint glass, half a part of borax, the same of oxide of tin, and one-twenty-fifth of a part of oxide of cobalt, melted together, made an enamel, which, when ground and applied as the others, fused with a less degree of heat. This, M. Rinman imagines, would have been acted upon in length of time by sulphuric acid. The oxide of cobalt was prepared by saturating a solution of cobalt in aqua-fortis with common salt, and evaporating to dryness
As these would not do for iron, he tried the following : 1. minium, nine parts ; flint glass, six ; pure potash, two; nitre, two ; borax, one ; were ground to- gether, put into a covered crucible, which they only half filled, and fused into glass. This poured out on a piece of marble, quenched in water, powdered and made into a thin paste, was laid on both sides of an iron vessel. After hav- ing been dried and heated gradually, the vessel was put under a muiHe, well heated in an assaying furnace, and in half a mi- nute the enamel melted. The vessel being then withdrawn, was found ena- melled of a beautiful black colour, which appeared to be ov ing to a thin layer of oxided iron seen through the transpa- rent glaze. 2. The same, with one hun- dreth part of oxide of cobalt prepared as above, covered the vessel more per- fectly with a blue enamel. 3. The same, ground with potters' white lead, which consists of four parts of lead and one of tin, produced a very smooth grey enamel more firm and hard than the preceding. A small quantity of red oxide of iron gave it a fine dark red colour. 4. Flint glass, twelve parts ; minium, eighteen ; potash, four; nitre, four ; borax, two ; oxide of tin, three ; oxide of cobalt, one eighth of a part; gave a smooth pearl coloured enamel, not brittle or subject to crack, and capable of enduring sud- den changes of heat and cold, as well as the action of oils, alkalies, and weak acids : but it cannot resist the stronger vegetable acids, and still less the mine- ral.
These enamels were applied only on hammered iron, cast iron being too thick to be heated with sufficient quickness. But they have been applied to the thin cast vessels in England. It seems unne-
cessary to add, none of them will bear hard blows ; and this is perhaps the rea- son why they have not been more used with us.
The application of enamel colours to glass or earthenware constitutes a pecu- liar branch of the art. M. Brougniart, of the porcelain manufactory at Sevres, has given a good account of them. (Ni- cholson's Journal, Vol. HI. 4to.)
These bodies may be divided into three very distinct classes, from the nature of the substances that compose them, the effects produced on them by the colours, and the changes they undergo. These are, 1. enamel ; soft porcelain, and all the glazes, enamels, or glasses, which contain lead in any considerable quantity. 2. Hard porcelain, or such as is glazed with feldspar. 3. Glass, in which there is no lead, such as the common window glass. The principles of composition of these colours, and the general phenome- na they present on these three grounds or supporters, are regularly treated of.
Colours in enamel painting have been longest known. Enamel is a glass ren- dered opaque by oxide of tin, and very fusible by the oxide of lead. It is this last, which, in particular, gives it proper- ties very different from those of the other excipients of metallic colours. Hence all the glasses and glazes which contain lead have the properties of enamel, and what we may assert of the one will apply to the other with very little difference.
Such are the white and transparent glazes of Dutch or Delf ware; and the glaze of the porcelain called soft ware.
This porcelain, the first made in France, particularly at Sevres, and in- deed for a long time almost exclusively at that manufactory, has for its base vi- treous frit, nearly opaque, capable of be- ing acted upon by marie, and its glaze is very transparent glass, containing much lead.
The colours made use of are the same as those for enameling, consequently the changes these colours undergo in enamel must take place in this species of porce- lain : the causes of the change being the same in both.
The colours for enamel and soft por- celain require less flux than the others, because the glass on which they are placed softens sufficiently to be pene- trated by them.
This solvent may be either the mix- ture of glass of lead and pure silex, call- ed rocaille, or this same glass mixed with that of borax.
ENAMELLING.
Montamy says, that glass of lead ought not to be used in the flux or enamel ; he employs borax alone. He then dilutes or makes up his colours in a volatile oil.
On the contrary, the painters of the ma- nufactory at Sevres use only colours with- out borax, because they dilute them with gum, and borax does not dilute them well this way. M. Brougn.art is convinced that both methods are equally good, and that Montamy is not justified in exclud- ing the fluxes of lead, as they are em- ployed without inconvenience every day, and even render the management of co- lours more easy.
It is remarked, that in the baking of these colours the glaze is softened so much as to be easily penetrated by them ; and this is one great cause of the change they undergo. They become diluted by the mixture with the glaze, and the first fire changes a painting, apparently finish- ed, into a very slight sketch.
The oxide of lead contained in the glaze is a more powerful cause of the great changes these colours undergo. Its destructive action is principally exercis- ed on the reds of iron, and is very re- markable.
It has already been shewn that the two principal causes of the change, which co- lours on enamel and tender porcelain un- dergo, do not relate to the composition of these colours, but entirely to the na- ture of the glass on which theyare placed. The assertion that the colours of porce- lain are subject to considerable change, relates to the colours of soft porcelain, a species of ware now almost totally aban- doned.
Hence it follows, that the paintings of porcelain require to be several times re- touched and burned, in order to possess the necessary strength. Though these paintings have always a certain softness, they are constantly more brilliant, and never subject to the inconvenience of scaling off.
Hard porcelain is the second species of ground or excipient for the metallic colours. It is known that the base of this porcelain is a very white argil, call- ed kaolin, mixed with a siliceous and calcareous solvent, and the glaze is no- thing but feldspar fused without an atom of lead.
This porcelain, which is that of Saxony, is of a much later date at Sevres than the soft or tender. The colours employed are of two kinds ; the first, used for re- presenting different objects, are baked with a very inferior fire to that required
for baking the porcelain itself. They are verv numerous and varied
The others, winch require to be fused at as great a heat as that for baking the porcelain, are laid on the general surface. They are much less numerous.
The colours for painting are made up very nearly of the same materials as those for tender porcelain ; they only contain more flux. This flux is compossd of the glass ot'lead (called rocuille) and of bo- rax. M. Brougniart asserts, that he has not met with any work that treats of the composition, use, and effects of these co- lours. In fact, it has no where been as- serted, in print, that all these colours, except one, are unchangeable in fire ; whereas it has been often asserted, in books, that paintings in enamel are sub- ject to considerable change.
When the porcelain is put into the fire to bake the colours, the feldspar glaze dilates and opens in pores, but does not become soft. As the colours do not penetrate it, they are not subject to the changes they undergo on tender porce- lain. It must, however, be observed, that they lose a little of their intensity by ac- quiring the transparence given them by the fusion.
When works of little importance are made, they need not be retouched ; but this is necessary when a painting is to be highly finished. This retouching is not more'distinguishable in paintings on por- celain, than in that of any other species of painting.
One of the great inconveniences of these colours is, that they scale or fly off when the fire is often applied.
This has been particularly remarked at Sevres, on account of the solidity and infusibility with which porcelain is there manufactured. But these qual ities cause it to resist the alterations of heat and cold for a longer time, and give its ground a more brilliant colour. On the other hand, the porcelains of Paris being more vitre- ous, transparent, and of a bluish cast, generally crack, if boiling water is fre- quently poured into them.
In order to remedy this evil, without altering the quality of the body, Broug- niart softens the glaze a little, by intro- ducing more siliceous or calcareous flux, according to the nature of the feldspar. This method succeeded, and for twelve months then past the colours had past two and three times through the fires, without cracking, provided there were not too much flux, and they were not laid on too thick.
ENAMELLING.
It has been remarked, that when soda and potash have been introduced, the co- lours scaled, so that they cannot be used as fluxes. These alkalies, being vola- tilized, abandon the colours which can- not adhere to the glaze by themselves.
It has been observed, that other co- lours are likewise prepared, which be- ing laid upon the general surface, are fused by the same fire as bakes the por- celain. These colours are but few, be- cause there are few metallic oxides that can support such a fire without being vo- latilized or discoloured. Their solvent is the feldspar. As they incorporate with the glaze they never crack, and are more brilliant.
The third receptacle of metallic vitri- fiable colours is glass without lead.
The application of these colours con- stitutes the art of painting upon glass ; an art much practised in former ages, but •which was, till lately, supposed to be lost, because out of fashion. It, however, too immediately depends on the art of painting on enamel and porcelain to be lost. Descriptions of the processes may be found in different books.
A book, entitled " L'Origine de Part de la Peinture sur Verre," published at Paris in the year 1693, and " Le Traite" de I'art de la Verriere," by Neri and Kunckel, seem to be the first works con- taining complete descriptions of this art. Those published since, even the great work of Leviel, which constitutes part of " Les Arts et Metiers," of thefFrench academy, and of the " Encyclopedic Me- thodique," are only compilations from the two former works.
It is somewhat remarkable, that if we follow the processes exactly as they are described in these works, as our author has done with some of them, the colours of which they pretend to give the re- ceipt, would never be fabricated. They only serve to show an able practitioner the method, and leave it to him to cor- rect or make additions. This was found to be the case by Citizen Meraud, who was engaged to prepare them for the manufactory of Sevres. He was obliged to make the colours for painting on glass rather from his own experience, than from the instructions in the work just mentioned.
The materials and fluxes which enter into the compositions of the colours for painting on glass are, in general, the same as those applied to porcelain. They vary only in their proportions; but a great number of the colours used for
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enamel and porcelain cannot lie applied on glass; many of them, when seen by transmitted light, entirely change their aspect, and exhibit an obscure tint, which can be of no use when deprived of- the white ground which throws them out. We shall point out these when we treat of the colours in particular. Those co- lours which can be used on this body sometimes change in the baking, and ac- quire a great transparency. They are generally beautiful only when placed be- tween the eye and the light, and they answer the purpose intended in painting glass.
There is more difficulty in baking- plates of coloured glass than is common- ly thought. The bending of the piece and the alteration of the colours are to be avoided. All the treatises we have con- sulted recommend the use of gypsum. This method sometimes succeeded with Brougniart, but generally the glass be- came white, and cracked in all direc- tions. It appears, that the glasses which are too alkaline, and which are far the most common in clear white glasses, are attacked by the hot sulphuric acid of the sulphate of lime. He was able with ease to bake much larger glasses than any before painted, by placing them on very smooth plates of earth or unglazed por- celain.
Concerning the several particular Colours.
After having collected the several phenomena which each class of verifiable colours offer, with regard to the bodies on which they are placed, we must shew the particular and most interesting phe- nomena, which every principal species of colours employed on tender porcelain, on glass, and in the fire that bakes the porcelain, present.
Concerning- the Reds, Purples, and Violets, obtained from Gold.
The carmine-red is obtained from the purple precipitate of Cassius. It is mix- ed with about six parts of its flux, and this mixture is directly employed without being first fused. It is then of a dirty violet, but acquires the beautiful car- mine by baking. It is however very deli- cate ; a little too much heat or carbonat- ed vapours easily spoil it ; yet it is more beautiful when baked with charcoal than with wood.
This colour, and the purple, which dif-
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fers little from it, as well as the shades which are obtained from their mixture with other colours, really change in all porcelains, and in the hands of all opera- tors. But this is the only one which changes on hard porcelain. It may be replaced by a substitution of rose-co- lour from iron, which does not change ; so that by excluding from the pallet the carmine made from gold, and substitut- ing the rose-coloured oxide of iron here spoken of, we have a pallet composed of colours, none of which are subject 10 any remarkable change. The rose-coloured oxide of iron has been long known, but was not employed on enamel, because it is then subject to considerable change. Or, perhaps, when the painters on ena- mel became painters on porcelain, they continued to work according to their an- cient method.
It might be supposed, that by previous- ly reducing the colour flamed carmine, already mixed with its solvent into a vitreous matter, the last tint would be obtained; but the fire which must be used to melt this vitreous mass destroys the red colour. Besides, it is found, that, to obtain this colour in perfection, it is necessary to pass it through the fire as little as possible.
The carmine of tender porcelain is made of fulminating gold, gently decom- posed, and muriate of silver ; there is no tin in it, which proves it is not necessary, for the fabrication of a purple colour, that the oxide of this last metal and that of gold should be combined.
Violet is likewise obtained from the purple oxide of gold. This colour pro- ceeds from having a greater quantity of lead in the flux, and it is nearly of the same tint, whether crude or baked.
These three colours totally disappear in the strong fire necessary to bake por- celain.
Carmine and purple afforded, upon glass, only tints of dirty violet. The vio- let, on the contrary, has a beautiful ef- fect, but is subject to change to blue.
Concerning the Red, Rose, and JJrmvn Colours, obtained from Iron.
These colours are made from red ozydated iron, prepared with nitric acid. The oxides are calcined still more by exposing them to the action of fire. If too much heated, they change to a brown.
Their flux is composed of borax and minium in small quantity.
These are the oxides which afford the rose and red colours, which may be sub- stituted instead of the same colours made from oxide of gold. If properly applied on hard porcelain, they never change. Brougman made roses with these colours, and there was no difference between the flower, before and after baking, except the brilliancy which colours naturally receive from fusion.
The colours may either be previously fused or not, at pleasure.
In a violent fire, they either partly disappear, or produce a dull and brick- dust red colour, which is not at all agree- able.
Their composition is the same, either for tender porcelain or for glass. They do not change on the latter, but on the former they almost entirely disappear by the first fire; and they must be laid on very heavily, in order to have any part visible.
It is to the presence of lead in their glaze that this singular effect must be at- tributed. Brougman ascertained this by a very simple experiment. He placed this colour on window glass, and fired it very strongly., and it did not change . He then covered some parts of it with minium, and again exposed it to the fire. The colours totally disappeared in those places where the red oxide of lead had been applied. When this experiment was performed on a larger scale, in a closed vessel, a large quantity of oxy- gen gas was disengaged.
This observation seems clearly to prove the effect of oxydatedlead as a dis- colourer of glass. We see that it does not operate, as has been supposed, by burning combustible impurities in the glass, but by dissolving, discolouring, and volatilizing the oxide of iron, which may affect its clearness.
Concerning the Yellotvs.
Yellows are colours which require much precaution in fabricating, on ac- count of the lead they contain ; which, sometimes, by approaching to the metal- lic state, produces black spots.
The yellows of hard and tender porce- lain are the same. They are composed of oxide of lead, white oxide of antimony, and sand. Oxide of tin is sometimes added; and when it is required very lively, and resembling the colour of mari- gold, red oxide of iron is added, the very deep colour of which disappears during: the previous fusion they undergo, on ac-
ENAMELLING.
count of the lead contained in this yel- low. When these colours are once made, they do not change : they disap- pear almost entirely in the porcelain fire- yellows.
These cannot be applied to glass ; they are opaque and muddy. That employed by the ancient painters on glass is, on the contrary, beautifully transparent, very brilliant, and of a, colour approaching gold. The processes they give indicate that it contains a mixture of silver; but when exactly followed they afford no- thing satisfactory. Citizen Meraud suc- ceeded in making it as beautiful as the ancient painters on glass, by employing muriate of silver, oxide of zinc, white clay, and the yellow oxide of iron. These colours are applied to glass simply ground, and without flux. The oxide of iron gives the yellow nearly the same tinge as it ought to have after the baking, and contributes, with the clay and oxide of zinc, to decompose the muriate of sil- ver without disoxydating the silver itself. A powder remains after baking, which does not penetrate the glass, and may be easily cleared off.
This yellow when employed in greater quantities affords deeper shades, and pro- duces a reddish colour.
Concerning the Blues.
These are known to be obtained from the oxide of cobalt ; their preparation is known to every chemist. The superiori- ty at Sevres, so justly reputed for the superiority of its blues, is owing mere- ly to the care taken in its fabrication, and to the quality of the porcelain, which appears more proper to receive it, on account of the violent fire it can support.
Brougniart observed one fact respect- ing the oxide of cobalt, which is, perhaps, not known to every chemist. It is vola- tile in a violent heat ; to this property must be attributed the bluish tint which the white (bordering upon blue) always receives. A white piece was purpose- ly put in the same case next to a blue ; the side of the white piece which was turned towards the blue became very bluish.
The blue of hard porcelain, prepared for what is called a blue ground by strong fire, is fused with feldspar ; the solvent for tender porcelain is silex, pot- ash, and lead ; it is not volatilized like the preceding, because the fire is much inferior to that of the hard porcelain.
These colours, being previously fus^ ed, do not in the least change when ap- plied.
The blues for glass are the same as for tender porcelain.
Concerning Greens.
The greens employed in painting are made with the green oxide of copper, or sometimes with a mixture of yellow and blue. They must be previously melted with their flux ; without this precaution, they would become black : but they do not change after the first fusion.
They must not be treated with a vio- lent fire, or they would totally disappear. The green grounds by strong heat are made with the oxides of cobalt and nick- el, but it is only a brownish green.
The bluish greens, named sky-blue, formerly a colour very much in esteem, can only be used on tender porcelain ; they always scale off from hard porcelain, because there is potash in their composi- tion. These greens cannot be used on glass, because they afford a dirty colour ; it is necessary to put a yellow on one side, and a more or less pale blue on the other, in order to produce a green. This co- lour may likewise be fabricated, by mix- ing a blue with the yellow oxide of iron. Brougniart hoped to obtain a green from the oxide of chrome ; and the experi- ments he made promised to be attended with success. The pure chromate of lead, fixed on porcelain by means of a strong fire, afforded him a very deep and very fixed blue, of considerable beauty.
Concerning Bistres and JJrovvn Reds.
These are obtained by mixtures of dif- ferent proportions of manganese, brown oxide of copper, and the oxide of iron, called umber. They are likewise pre- viously fused in their solvents, so that they do not in the least change on ten- der porcelain, lead not having the same action on the oxide of manganese as it has on that of iron. This colour may be employed very well on glass.
The brown red, ground by strong heat, known by the name of fonds caille, are made in the same manner : feldspar is their flux. There is no titanium in their composition, though generally asserted in books. Titanium was not known at Sevres when Brougniart first came to that manufactory. He treated this singular metal in various ways, and never ob- tained any grounds but a slight obscure yellow, and very uncertain in its quality.
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Concerning the J3lack$.
Black colours are the most difficult to be obtained very beautiful. There is no metallic oxide, which, singly, affords a fine black. Manganese gives the best ; iron, an opaque, dull, blistered black, which easily turns to red. The makers of colours have therefore combined se- veral metallic oxides, which, singly, do not afford blacks, and they have obtained a very beautiful colour, but it is subject to scale and become dull.
The oxides are, those of manganese, the brown oxides of copper, and a little of that of cobalt. Grey is obtained by suppressing the quantity of copper and increasing the quantity of flux.
The Sevres manufactory is the only one which has as yet produced beautiful blacks with a strong fire. This is more owing to the quality of the biscuit, than to any peculiarity of process. It is by a mixture of blue with the oxides of man- ganese and iron that they make this very brilliant black.
The blacks for opaque glass are made the same as for painting, by giving dif- ferent doses of solvent.
After the display of the principles of fa- bricating each principal colour, it is clear, that by mixing these colours all possible shades may be obtained : and also that care in the preparation, choice of mate- rials, and just proportions of closes, must exhibit very sensible differences to the experienced eye of a painter. A know- ledge of the composition of colours does not give the requisite care and neatness in making them up.
On recapitulating the facts here just stated, in order to present them in a ge- neral view, we see, first, that amongst the colours usually employed for hard porcelain, one only is susceptible of change, namely, the carmine : and this may be replaced by the reds of iron, and then no colour changes.
M. Brougniart presented to the Insti- tute an unbaked head made in this man- ner, and a painting of two roses, the one baked, and the other in its first state. There was not any difference between them.
Secondly, That amongst the colours of soft? porcelain and enamel, several change considerably, particularly the reds of iron and gold, with the yellows, greens, and browns. None have been substituted instead of them, this species 4>f painting being almost abandoned.
Thirdly, That several of these colours
change likewise upon the glass by be- coming perfectly transparent, particular- ly the yellows and violets.
Fourthly, That neither an additional calcination, nor an additional fusion, as has been suspected, will prevent them from changing : for this method alters the colours that change, and does no- thing to the rest. The change which se- veral colours undergo on tender porce- lain, and on glass, does not therefore re- late to the nature of their composition, but rather to that of the body on which they are placed. Consequently, by sup- pressing the carmine of gold from the- colours of hard porcelain, we shall have a series of unchangeable colours.
ENARGEA, in botany, a genus of the Hexandria Monogynia class and order. Essential character : calyx none ; petals six, oblong, ovate, concave, acute, three outer, three inner, green spotted ; berry three-celled, with four or five globular seeds. There is but one species, viz. E. marginata, a native of Terra Del Fuego.
ENCALYPTA, in botany, a genus of the Cryptogamia Musci class and order. Capsule cylindrical ; fringe simple, of sixteen linear erect distinct teeth ; veil campanulate, inflated, lax. There are six species.
ENCAUSTIC, the same with enamel- ling and enamel. See ENAMELLING.
ENCAUSTIC painting, a method of paint- ing made use of by the ancients, in which wax was employed to give a gloss to their colours, and to preserve them from the injuries of the air.
ENCHASING, or CHASING, the art of enriching and beautifying gold, silver, and other metal work, by some design, or figures represented thereon, in low relievo. See RELIEVO and SCULPTURE.
Enchasing is practised only on hollow thin works, as watch-cases, cane-heads, tweezer-cases, or the like. It is per- formed by punching or driving out the metal, to form the figure from within side, so as to stand out prominent from the plane or surface of the metal. In order to this they provide a number of fine steel blocks, or puncheons, of divers sizes ; and the design being drawn on the surface of the metal, they apply the inside upon the beads or tops of these blocks, directly under the lines or parts of the figures ; then with a fine hammer, striking on the metal sustained by the block, the metal yields, and the block makes an indenture or cavity on the in- side, corresponding to which 'there is a
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prominence on the outside, which is to stand for that part of the figure.
Thus the workman proceeds to chase and finish all the parts, by successive ap- plication of the block and hammer to the several parts of the design. And it is wonderful to consider with what beauty and justness, by this simple piece of me- chanism, the artist in this kind will re- present foliages, grotesques, animals, his- tories, &c.
ENCHELIS, in natural history, a ge- nus of the Vermes Infusoria. Worm in- visible to the naked eye, very simple, cy- lindrical. There are fifteen species. An account of these may be found in Adams " On the Microscope." ,
ENCROACHMENT, in law, an unlaw- ful gaining upon the rights or possessions of another. It is generally applied to the unlawful occupation of wastes and com- mons.
ENDEAVOUR, where one endeavours actually to commit felony, &c. he is pun- ishable as for a misdemeanour ; and an assault, with intent to rob, is punished by transportation. Statute 7 Geo. II. c. 21,.
EN DEC AGON, a plane geometrical fi- gure of eleven sides and eleven angles, if each side of this figure be 1, its area will be 9.3656399=i4iofthe tangents of /3_7r degrees to the radius one.
ENDEMIC, or ENDKMICAL diseases, those to which the inhabitants of pariicu- lar countries are subject more than others, on account of the air, water, situation, and manner of living.
ENDIVE, in botany, &c. broad-leaved succory. SeeCicHomuM.
ENDOWMENT, in law, is the widow's portion ; being a third part of all the free- hold lands and tenements, of which her husband was seized at any time during the coverture. Of lands, not freehold, her portion varies, according to the custom in different places.
ENEMY, in law, an alien, or foreigner, who in a public capacity invades any country, and who cannot be punished as a traitor, but must be subjected to martial law. An alien residing in Eng- land, under the protection of the king's peace, may be dealt with as a traitor, be- cause he owes a qualified allegiance.
ENFRANCHISEMENT, in law, the in- corporating a person into any society or body politic; such as the enfranchisement of one made a citizen of London or other city, or burgess of any town corporate, because he is made partaker of its liber- ties or franchises.
ENGINE, in mechanics, is a compound machine made of one or more mechani- cal powers, as levers, pullies, screws, &c. in order to raise, cast, or sustain any weight, or produce any effect, which could not be easily effected otherwise.
Engines are extremely numerous ; some used in war, as the battering ram, balista, waggons, chariots, &c. others in trade and manufactures, as cranes, mills, presses, &c. ; others to measure time, as clocks, watches, &c. ; and others for the illustra- tion of some branch of science, as the or- rery, cometarium, and the like.
In general, we may observe, concerning1 engines, that they consist of one, two, or more of the simple powers variously com- bined together ; that in most of them the axis in peritrochio, the lever, and the screw, are the constituent parts ; that in all a certain power is applied to produce an effect of much greater moment ; and that the greatest effect or perfection is when it is set to work with four-ninths of that charge which is equivalent to the power, or will but just keep the machine inequilibrio
In all machines the power will just sus tain the weight, when they are in the in- verse ratio of their distances from the centre of motion.
ESGJNE, jire, by Rowntree. We have selected an engine by this maker to give a drawing and description, as it is greatly superior to the common engine with two force pumps. As that kind of engine has so often been described by various au- thors, and its principles so essily compre- hended from the description of a force- pump, we judge it unnecessary to give any drawing of it.
The fire engine by Rowntree is a dou- ble force-pump, of a peculiar construc- tion, similar in its action to the beer en- gine, (described under that article,) but as it is on a much larger scale, its con- structions, are of course varied. Plate Rowntree's engine, fig. 1 and 2, are two elevations at right angles to each other, of the external part of the engine mount- ed on four wheels. Fig. 3 and 4, are two sections, perpendicular to each other, of the body of the engine or pump: fig. 5 and 6, are parts of the engine. The same letters are used as far as they apply in all the figures, A, A, A, A ; fig. 3 and 4, is a cast-iron cylinder truly bored ; it is ten inches diameter and fifteen long, it has a flanch at each end, whereon to screw two covers, with stuffing boxes, a, a, in their centres, through which the spindle, B, 13, of the engine passes, ancl being
ENGINE.
packed with hemp round the collar, makes a tight joint ; the piston, D, is affixed to the spindle within the cylinder, and fits it tight all round by means of leathers, applied as described in the beer- engine ; at E, fig. 4, a partition, called a saddle, is fixed in the cylinder, and fits against the back of the spindle tight by a leather.
We have now a cylinder divided by the saddle, E, and piston, into two parts, whose capacity can be increased and di- minished by movir.g the piston, with pro- per passages and valves to bring and con- vey away the water: this will form a pump. These passages are cast in one piece with the cylinder : one, d, for bring- ing the water, is square, and extends about | round the cylinder; it connects at bottom with a pipe, e ; at its two upper ends opens into two large chambers,/^, extending near the whole length of the cylinder, and closed by covers, h A, screwed on : i k, are square openings (shown by clotted squares in fig. 3. ) in the cylinder, communicating with the cham- bers : / ff, I m, .are two valves, closing their ends of the curved passage, c7, and preventing any water returning down the passage, d: n o, are two passages from the top of the cylinder, to convey away the water ; they come out in the top ofthe cylinder, which, together with the top of the chambers,/,^, form a large, flat sur- face, and are covered by two valves, p yt to retain the water which has passed through them. A chamber, K, is screw- ed over these valves : and has the air vessel k, fig. 1 and 2, screwed into its top ; from each side of this chamber a pipe, iv iv, proceeds, to which a hose is screwed, as shown in fig. 1. Levers, x x, are fixed to the spindle at each end, as shown in fig. 1, and carry the handles, H H, by which men work the engine. U hen the piston moves, as shown by the arrow in fig. 4, it produces a vacuum in chamber,/, and that part ofthe cylinder contiguous to it ; the water in the pipe, e, then opens the valve, m, and fills the cylinder. The same motion forces the water contained in the other part of the cylinder through the valve, q, into cham- ber, K, and thence to the hose through the pipe, w; the piston being turned the other way reverses the operation, with respect to the valves, though it continues the same in itself. The pipe, e, is screw- ed by a flanch to an upright pipe, P, fig. 5, connected with another squareiron pipe, fastened along the bottom of the chest of the engine : a curved brass tube,
G, comes from this pipe, through the end ofthe chest, and is cut into a screw, to fit on the suction hose, when it can be used ; at.other times a close cap is screw- ed on, and another brass cap at H, within the chest, is screwed upwards on its socket, to open several small holes made in it, and allow the water to enter into the pipe ; in this case the engine chest must be kept full of water by buckets. The valves are made of brass, and turn upon hinges. The principal advantage of the engine is the facility with which it is cleaned from any sand, gravel, or other obstructions, which a fire-engine will al- ways gather when at work.
The chambers, /,_§-, being so large, al- low sufficient room to lodge a greater quantity of dirt than is likely to be accu- mulated in the use of the engine at any one fire ; and if any of it accidently falls into the cylinder, it is gently lifted out again into the chambers by the piston, without being any obstruction to its mo- tion : to clear the engine from the dirt, two circular plates, r r, five inches diame- ter, are unscrewed from the lids, h h, of the chambers/ g, and when cleaned are screwed on again : these screw covers fit perfectly tight without leather, and can be taken out, the engine cleared, and enclosed again in a very short time, even when the engine is in use, if found ne- cessary.
The two upper valves, p q, and cham- ber, K, can also be cleared with equal ease, by screwing out the air vessel, k k, fig. 1, which opens an aperture of five inches, and fits air-tight, without leather, when closed. The valves may be repair- ed through the same openings. ' The use of the air-vessel k k, fig. 1 and 2, is to equalize the jet from the engine during the short intennittance of motion at the return of the piston stroke : this it does by the elasticity of the compressed air within it, which forces the water out con- tinually, though not supplied quite regu- larly from the engine.
The engine from which our drawing was taken was made for the Sun Fire Insurance Company, in London, and from some experiments made by their agent, Mr. Samuel Hubert, appears to answer every purpose.
EJTGIXE, for raising -water. The frame ofthe machine is of cast iron, nearly in the form of the letter A; there are two of these frames, B B, (fig. 1, Plate Pump- Engine,) screwed together by means of five wrought iron pillars, a a a 'a ; D is another smallerframe, to support the axis
ENGINE.
of the fly wheel, connected with the other frame by three short pillars; E, is the fly wheel, turned by winches on the end of its axis; it has a pinion (13) of 13 leaves upon its axis, turning a wheel (48) of 48 teeth, on whose axis are two cranks b, b, opposite to each other, to work the pumps : e e, are the two crank rods, made each in two branches, and jointed at the lower end into two other rods,//, which slide through holes made in the fixed bars, gg, fig. 2; the crank rods receive these bars between their two branches, and by this means, though the rods, //, are confined by their guides to move truly vertical, the crank rods, e e, can partake of the irregular motion of the crank. The pump rods of the pumps are screwed to the rods,//, by two nuts, and go down into the pumps, G H, sup- ported from the iron frame by eight iron braces, h h. The pumps consist of two barrels, G H, with valves at the bottom, allowing water to enter them freely, but preventing its return ; the buckets fixed to the pump rods fit the barrels truly, and have valves in them shutting downwards ; I, is a chest bringing water to the valves in the bottom of the barrels ; K, is another, communicating with the top of the bar- rels by two crooked passages, to carry away the water from them ; the barrels are close at top, and the pump rods pass through close stuffing boxes, through which no water will leak by them. The action of the pump is the same as the common sucking pump : when the bucket is drawn up, the valve in it closes, and it forms a vacuum in the lower part, of the barrel; this causes the water to ascend into it through the chest, I, to restore the equilibrium ; at the same time it raises all the water which was above it through the chest, K ; on the descent of the bucket the valve at the bottom of the barrel shuts, and prevents the escape of the water; the valve in the bucket opens, and the water passes through it, ready to be raised at the next stroke. The barrels in ques- tion are 3J inches diameter, and 8 inches stroke. As the two cranks, 6, 6, are op- posite each other, when one bucket is rising, the other is going down ; by this means the power required to turn the machine by the handles is equalized, and also the quantity of water raised by the engine.
Engines for raising water, by the pres- sure and descent of a column inclosed in a pipe, have been lately erected in dif- ferent parts of the country. The prin- ciple now adverted to was adopted in
some machinery executed in France abou' 1731, and was likewise adopted in Corn- wall more than forty years ago ; but the pressure engine, of which we are about to give a particular decription, is the in- vention of Mr. R Trevithick, who pro- bably was not aware that any thing at all similar had been attempted before. This engine, a section of which, on a scale of id of an hich to a foot, is shewn in Plate Pressure-Engines; one was erected about eight years ago at the Druid copper mine, in the parish of Illogan, near Truro. A B, represents a pipe six inches in diameter, through which water descends from the head to the place of its delivery, to run off by an adit at S, through a fall of 34 fathoms in the whole ; that is to say, in a close pipe ^Lown the slope of a hill 200 fathoms longy with 26 fathoms fall; then perpendicularly six fathoms, till it arrives at B, and thence through the engine from B to S two fathoms ; at the turn B, the water enters into a chamber, C, the lower part of which terminates in two brass cylinders, four inches in diameter ; in which two plugs or pistons of lead, D and E, are capable of moving up and down by their piston rods, which pass through a close packing above, and are attached to the extremities of a chain leading over and properly attached to the wheel Q, so that it cannot slip.
The leaden pieces, D and E, are cast in their places, and have no packing what- ever. They move very easily; and if at any time they should become loose, they may be spread out by a few blows with a proper instrument, without taking them out of their place. On the side of the two brass cylinders, in which D and E move, there are square holes communicating towards G, with a horizontal trunk, or square pipe, four inches wide, and three inches deep. All the other pipes, G, G, and R, are six inches in diameter, except the principal cylinder wherein the piston, H, moves ; and this cylinder is ten inches in diameter, and admits a nine foot stroke.
The piston rod works through a stuf- fing-box above, and is attached to M N, which is the pit rod, or a perpendicular piece divided into two, so as to allow its alternate motion up and down, and leave a space between, without touching the fixed apparatus, or great cylinder. The pit rod is prolonged down in the mine> where it is employed to work the pump ; or, if the engine was applied to mill-work, or any other use, this rod would be the communication of the first mover, K L,
ENGINE.
is a tumbler, or tumbling bob, capable of being moved on the gudgeons, V, from its present position to another, in which the weight L, shall hang over with the same inclination on the opposite side of the perpendicular, and consequently the end, K, will then be as much depressed as it is now elevated.
The pipe, R S, has its lower end im- mersed in a cistern, by which means it delivers its water without the posibility of the external air introducing itself; so that it constitutes a Torricellian column, er water barometer, and renders the whole column from A to S effectual, as we shall see in our view of the opera- tion.
The operation. Let us suppose the lower bar, K V, of the tumbler to be horizontal, and the rod, P O, so situated, as that the plugs , or leaden pistons, D and E, shall lie opposite to each other, and stop the water ways, G and F. In this state of the engine, though each of these pistons is pressed by a force equi- valent to more than a thousand pounds, they will remain motionless, because these actions being contrary to each other, they are constantly in equilibrio. The great piston, H, being at the bottom of its cylinder, the tumbler is to be thrown by hand into the position here de- lineated. Its action upon O P, and con- sequently upon the wheel, Q, draws up the plug E, and depresses D, so that the water way, F, becomes open from A B, and that of G to the pipe R : the water consequently descends from A to C, thence to F, until it acts above the piston F. This pressure forces down the pis- ton, and if there be any water below the piston, it causes it to pass through G G G into R : during the fall of the piston, which carries the pit rod, M N, along with it, a sliding block of wood, I, (dot- ted) fixed to this rod, is brought into con- tact with the tail, K, of the tumbler, and lowers it to the horizontal position, be- yond which it oversets by the acquired motion of the weight L.
The mere rising of the piston, if there was no additional motion in the tumbler, would only bring the two plugs, D and E, to the position of rest, namely, to close G and F, and then the engine would stop ; but the fall of the tumbler carries the plug, D, upwards, quite clear of the hole, F, and the other plug, E, down- wards, quite clear of the hole, G : these motions require no consumption of power, because the plugs are in equilibrio, as was just observed. In this new situation
the column, A B, no longer commufti cates with F, but acts through G upon the lower part of the piston H, and raises it ; while the contents of the great cylin- der above that piston are driven out through F, and pass through the open- ing at D into R. It may be observed, that the column which acts against the piston is assisted by the pressure of the atmosphere, rendered active by the co- lumn of water hanging in R, to "vvhich that assisting pressure is equivalent, as has already been noticed. When the piston has ascended through a certain length, another slide or block upon the pit-rod (not seen) applies against the tail, K, of the tumbler, which it raises and again oversets, producing once more the posi- tion of the plugs D E, here delineated, and the consequent descent of the great piston H, as before described. The de- scent produced the former effect on the tumbler and plugs, and in this manner it is evident that the alternations will go on without limit, or until the manager shall think fit to place the tumbler and plugs, D E, in the positions of rest, namely, so as to stop the passages, F and G. The length of the stroke may be varied by altering the positions of the pieces, I, and the other lower down, which will shorten the stroke, the nearer they are together ; as in that case they will sooner alternate upon the tail, K, As the sudden stoppage of the descent of the column, A B, at the instant when the two plugs were both in the water- way, might jar and shake the apparatus, those plugs are made half an inch shorter than the depth of the side holes, so that in that case the water can escape directly through both the small cylinders to R. This gives a moment of time for the ge- neration of the contrary motion in the piston, and the water in G G G, and greatly deadens the concussion which might else be produced. See STEAM; ENGINE.
Some former attempts to make pres- sure engines upon the principle of the steam-engine have failed ; because water, not being elastic, could not be made to carry the piston onwards a little, so as completely to shut one set of valves and open another; in the present judicious construction, the tumbler performs the office of the expansive force of steam at the end of the stroke.
ENGINE for driving piles, used at building Westminster bridge, is con- structed as follows : A, (Plate V. Miscel. fig. 3.) is the great shaft, on which are
ENG
ENG
the great wheel and drum : B, the great wheel with cogs, that turns a trundle head with a fly, to prevent the horse's falling when the ram is discharged; C, the drum on which the great rope is wound ; D the follower (with a roller at one corner) in which are contained the tongs, to take hold of the ram, and are fastened to the other end of the great rope, which passes over the pulley, near the upper end of the guides, between which the ram falls ; E, the inclined planes, which serve to open the tongs, and discharge the ram ; F, the spiral barrel that is fixed to the drum, on which is wound a rope with a counter- poise, to hinder the follower from acce- lerating, when it falls down to take up the ram ; G, the great bolt which locks the drum to the great wheel ; H, the small lever, which has a weight fixed at one end, passes through the great shaft below the great wheel, and always tends to push the great bolt upwards, and lock the drum to the great wheel ? I, the forcing bar, which passes through the hollow axis of the great shaft, bears upon the small lever, and has near the upper end a catch, by which the crooked lever keeps it down ; K, the great lever, which presses down the forcing bar, and dis- charges the great bolt at the time the long end is lifted up by the follower ; L, the crooked lever, one end of which has a roller, that is pressed upon by the great rope, the other end bears upon the catch of the forcing bar during the time the follower is descending ; M, the spring that presses against the crooked lever, and discharges ,it from the catch of the forcing bar as soon as the great rope slackens, and gives liberty to the small lever to push up the bolt.
By the horse's going round, the great rope is wound about the drum, and the ram is drawn up, till the tongs come between the inclined planes, where they are opened, and the ram is dis- charged.
Immediately after the ram is discharg- ed, the roller, which is at one end of the follower, takes hold of the rope that is fastened to the long end of the great lever, and lifts it up ; the other end presses down the forcing bar, unlocks the drum, and the follower comes down by its own weight.
As soon as the follower touches the ram, the great rope slackens, and the spring, M, discharges the crooked lever from the catch of the forcing bar, and jjives liberty to the small lever to push
VOL. V.
up the great bolt, andto lock the drum to the great wheel, and the ram is drawn up again as before.
ENGINEER, in the military art, an able, expert man, who, by a perfect know- ledge in mathematics, delineates upon paper, or marks upon the ground, all sort of forts, and other works pro- per for offence and defence. He should understand the art of fortification, so as1 to be able, not only to discover the de- fects of a place, but to find a remedy proper for them, as also how to make an attack upon, as well as to defend, the place. Engineers are extremely neces- sary for these purposes : wherefore it is requisite that, besides being ingenious, they should be brave in proportion. When at a siege the engineers have nar- rowly surveyed the place, they are to make their report to the general, by ac- quainting him which part they judge the weakest, and where approaches may be made with most success. Their busi- ness is also to delineate the lines of cir- cumvallation and contrarallation, taking all the advantages of the ground; to mark out the trenches, places of arms, batteries, and lodgments, taking care that none of their works be flanked or discovered from the place. After making a faithful report to the gene- ral of what is doing, the engineers are to demand a sufficient number of work- men and utensils, and whatever else is necessary.
ENGRAFTING or GRAFTING, in gar- dening. See the article GRAFTING.
ENGRAILED, or INGRAILEP, in he- raldry, a term derived from the French, hail; and signifying a thing the hail has fallen upon and broke off the edges, leaving them ragged, or with half rounds, or semicircles, struck out of their edges.
ENGRAVING. This term is at pre- sent confined to the art of excavating copper and wood, in lines, in so judicious a manner, as to produce imitations of paintings and drawings when painted on paper. It is certain that engraving for the production of prints was unknown long after the practice of painting in oil had arrived to great perfection, but good prints are common from plates engraved in the fifteenth century, many of which are landscapes, most laboriously, and even excellently, performed by the gra- ver, although it is well known that the instrument just mentioned cannot freely express those serrated and serpentine lines, necessary for foliage and short
D
ENGRAVING.
grass intermixed with plants, since so admirably delineated in etchings. A gold- smith of Florence, named Maso Finiguer- ra, is said to have discovered the art ; but this assertion must undoubtedly merely apply to his obtaining1 impressions from lines engraved originally without the least idea of such a result ; were we to examine the subject closely, it might be proved, that outlines have been cut in metals, representing figures, &c. from the most remote periods of antiquity, but being subject to decay, they have not reached our time, as the more durable granites have done, embellished with hi- eroglyphics cut in them in a manner which might be printed on paper. Ar- guing from these premises, it may be in- ferred, that the ancients understood the art of engraving in metal, though without conceiving that the copies of their pro- ductions might be multiplied by means of ink on soft white cloth, or similar ma- ter als. Albert Durer, born in 1470, and who died at Nuremberg, 1528, is said to have been the first person on record claim- ing the name of an engraver in the long list of celebrated artists ; but certainly very excellent engraved brass figures, the lines filled with substances to show them more clearly, are now extant on tombs in some hundreds of churches in England, the dates of many of which are prior to the time of his birth. This fact will serve to prove that the printing of engraved plates was discovered between 1470 and 1528 ; indeed the perfection that engrav- ing had reached in the latter century plainly demonstrates, that the use of the graver was by no means a modern dis- covery. The encouragement of the fine arts has ever been a distinguishing trait of the inhabitants of the continent of Eu- rope ; it is not wonderful, therefore, that engraving closely followed the footsteps of the parent arts, and flourished there in greater perfection than in England, where they have been in a state ef mise- rable depression till within the last cen- tury, when literature was supposed to re- ceive some aid from the graver ; the book- sellers, taking the hint, have encouraged the predilection of the public, which has operated as a stimulus to the artist, and the consequence is, that the graphic em- bellishments of British topographical and poetical works are equal, if not superior, to any in Europe.
Historical engravings for the port fo- lio and furniture seemed at one period to advance rapicHy towards perfection, to which the late Alderman Boydell greatly
contributed; but the death of Str;i. Hall, and Woollet, have been almost fatal to the hopes of the amateur, which rests, in a great measure, upon Heath, Sharp, Bromley, and a few others, as in this par- ticular instance we do not include those eminent foreigners, who have or do at present reside in England. Whatever de- ficiencies we may discover in the prose- cution of the arts in this country is, fortunately, not to be attributed to want of genius, or relaxation from study, in the artist; the chill of apathy in the rich, who view a wretched coloured aquatint with the same or more pleasure than the most laboured production of the gra- ver, is the baleful cause of the languish- ing state of historical engraving. When persons capable of ''affording patronage are taught discrimination, future Wool- lets will fascinate the best judges of en- graving.
We shall now proceed to explain the methods of executing different descrip- tions of engraving. The graver, an in- strument of steel, is the primary object for engraving on copper; it is square for cutting of broad lines, and lozenge for the finest, and must be tempered to that exact state, which will prevent the point from breaking or wearing by its action on the metal ; to obtain this state, is is customary to heat it when too hard on the end of a red hot poker, till it assumes a straw co- lour, and then cool it in oil ; if held too long, it will become blue, soft, and use- less, till the process of tempering the steel is renewed. As it is possible a graver may be of the proper degree of solidity, except in som^ inconsiderable part, it would be well to rub it on the oil stone till that is ascertained. The graver is inserted in a handle of hard wood, re- sembling a pear with a longitudinal slice cut off, which is to enable the artist to use it as flat on the plate as his fingers and thumb will permit. In order to pre- pare this instrument for cutting a clear smooth line, great care must be taken, in sharpening it, that the original general form should be preserved, by laying the sides flat upon the oil-stone, and rubbing them so as not to round them in the least, after which the graver is to be held sloping towards the person, and rubbed thus till the point is extremely sharp ; besides these precautions, it will be necessary that the point should not be exactly in a right line with the lower part of the gra- ver, but a little higher, that it may not press too deep into the copper. In rub- bing the sides of the graver, the usual
ENGRAVING.
manner has been to confine the right arm close to the side, placing the fore finger of the left hand on the upper side of the tool when on the stone. This instrument is used for finishing1 the imperfections discoverable in etchings, and exclusively in engraving- writing.
The scraper is a long triangular piece of steel, tapering gradually from the han- dle to the point; the three edges produc- ed by this form, being sharpened on the oil-stone, are used for scraping off the roughness occasioned by the graver, and erasing erroneous lines.
The burnisher is a third instrument of steel, hard, round, and highly polished, for rubbing out punctures or scratches in the copper. The oil stone has been al- ready mentioned ; to those may be added the needle or dry point for etching, and making those extremely fine lines which cannot be done with the graver.
Cushions made of soft leather, and fill- ed with fine sand, hence called sand- bags, are required for the support of the plate in engraving, which, from their cir- cular surface, permit the copper to turn with ease, and facilitate the cutting of those true curves composing the shading of most subjects. The oil rubber and charcoal are necessary for polishing the plate.
Every thing depends upon the free use of the graver, therefore the utmost care must be taken to hold it properly, by pre- venting the interposition of the fingers be- tween the graver and the plate, with the fore finger on the upper angle, which enables the artist to conduct it parallel with the substance engraved, thus pre- venting the point from entering deeply, and impeding the progress of the tool.
To engrave well requires good materi- als, though those are nearly confined to two, the graver, and the best copper; the latter should be free from flaws, small punctures, well hammered to close the pores, and polished to such a degree as to be free from the slightest scratches.
To trace the design intended for en- graving accurately on the plate, it is usual to heat the latter sufficiently to melt white wax, with which it must' be cover- ed equally and thin, and suffered to cool ; the drawing is then copied in outlines with a black-lead pencil on paper, which is laid with the pencilled side upon the wax, and the back rubbed gently with the burnisher, which will transfer the lead to the wax. The design must next be traced with an etching needle through the wax on the copper, when, on wiping
it clean, it will exhibit all the outlines ready for the graver.
The table intended for engraving on should be perfectly steady, and the sand- bags placed equally firm* in cutting o curved or undulating lines, the graver must be held still, or moved, to suit the turning of the plate with the left hand ; but when straight lines are intended, the plate is to be held stationary, and the graver urged forward with more or less pressure, according to the thickness of the line. Great care is necessary to carry the hand with such steadiness and skill, as to prevent the end of the line from being stronger and deeper than the commencement ; and sufficiem space must be left between the lines, to enable the artist, to make those stronger, gradu- ally, which require it. The roughness or burr occasioned by the graver must be removed by the scraper, the lines filled by the oil-rubber, and the surface of the copper cleansed, in order that the progress of the work may be ascer- tained.
If any accident should occur, by the slipping of the graver beyond the boun- dary required, or lines are found to be placed erroneously, they are to be ef- faced by the burnjsher, which leaving1 deep indent ings, those must be levelled by the scraper, rubbed with charcoal and water, and finally polished lightly with the burnisher.
As the uninterrupted light of the day causes a glare upon the surface of the copper, hurtful and dazzling to the eyes, it is customary to engrave beneath the shade of silk paper, stretched on a square frame, which is placed reclining towards the room, near the sill of a window.
Such are the directions and means to be employed in engraving historical sub- jects ; indeed, the graver is equally ne- cessary for the completion of imperfec- tions in etching, to which must be added the use of the dry point in both, for making the faintest shades in the si.y, ar- chitecture, drapery, water &c. &c.
Engraving' of JWezzotmlos differs en- tirely from the manner above described ; this method of producing1 prints, which resemble drawing's in Indian ink. is sa.d by Evelyn, in ins history of chalcography, to have been discovered by Prince Ru- pert, and was some years pas., a very fa- vourite way of engraving poitraifs and historical subjects ; of the former, the large heads by Fry are of superior ex- cellence.
ENGRAVING,
The tools required for this easy and rapid mode of proceeding- are, the ground- ing-tool, the scraper, and the burnisher ; the copperplate should be prepared as if intended for the graver, and laid flat upon a table, with a piece of flannel spread under it, to prevent the plate from slip- ping- ; the grounding-tool is then held perpendicularly on it, and rocked with moderate pressure backwards and tor- wards, till the teeth of the tool have equally and regularly marked the copper from side to side; the operation is after- wards repeated from end to end, and from each corner to the opposite ; but it is ne- cessary to observe, that the tool must never be permitted to cut twice in the same place ; by this means the surface is converted into a rough chaos of intersec- tions, which, if covered with ink and printed, would present a perfectly black impression upon the paper.
To transfer the design to be scraped, it is usual to rub the rough side of the plate with a rag dipped into the scra- pings of black chalk, or to smoke it with burning wax taper, as in the process for etching ; the back of the design is then covered with a mixture of powdered red chalk and flake white, and laid on the plate through which it is traced ; parti- cles of red, in the form of the outlines, are thus conveyed to ilie black chalk on the plate, which are to be secured there by the marks of a blunted point ; the process must then be carried on with the scraper, by restoring the .plate in the perfectly light parts of the intended print to a smooth surface, from which' the gra- dations are preserved by scraping off more or less of the rough ground ; but the burnisher is necessary to polish the extreme edges of drapery, -.c., where the free touch of the brush in painting repre- sents a brilliant spot of light. The deep- est shades are sometimes etched and cor- roded by aquafortis, and so blended with the mezzotinto ground added afterwards, that there is nothing offensive to the eye in the combination.
Many proofs are required to ascertain whether the scraping approaches the de- sired effect, which is done by touching the deficient parts with white or black chalk, on one of the proofs from the original drawing, and then endeavouring to make the plate similar by further scraping, or relaying the ground with a small tool made for this particular pur- pose, where too much of the roughness has be en effaced.
Engraving on Steel is confined to the cutting of puncht-s, for the conveyance of any form a certain depth into that or any other metal, seals, and dyes, for im- pressing the designs of coins, medals, &,c . on gold, silver, or copper, &c. The punches are engraved from models in wax made in relievo, and, when com- pleted, are tempered to that degree of solidity, which will bear the violent blows, without blunting the finest parts or break- ing them, necessary to produce the ma- trix in the steel intended for striking of medals or coins, which must be heated to prevent such a disaster, and tempered again, for a similar reason to the preced- ing, after it is finished.
There are several tools used in finish- ing of dyes, which are, gravers, chissels, and flatters ; and many little punches for making ornamental borders and mould- ings to coins and medals ; the latter are always in greater relief than the former, and consequently more difficult to exe- cute in perfection.
Engraving on precious Stones is accom- plished with the diamond or emery. The diamond possesses the peculiar property of resisting every body in nature, and, though the hardest of all stones, it may be cut by a part of itself, and polished by its own particles. In order to render this splendid substance fit to perform the operations of the tool, two rough dia- monds are cemented fast to the ends of the same number of sticks, and rubbed together till the form is obtained for which they are intended ; the powder thus produced is preserved, and used for polishing them in a kind of mill fur- nished with a wheel of iron ; the diamond is then secured in a brazen dish, and the dust mixed with olive oil applied, the wheel is set in motion, and the friction occasions the polished surface so neces- sary to give their lustre due effect. Other stones, as rubies, topazes, and sapphires, are cut into various angles on a wheel of copper, and the material for polishing those is tripoli diluted with water.
A leaden wheel, covered with emery mixed with water, is preferred for the cutting of emeralds, amethysts, hya- cinths, agates, granites, &.c. 8cc. and they are polished on a pewter wheel with tripoli ; opal, lapis lazuli, &c.are polished on a wheel made of wood.
Contrary to the method used by per- sons who turn metals, in which the sub- stance to be wrought is fixed in the lathe, turned by it, and the tool held to the sub-
ENGRAVING.
stance, the engraver of the crystal, lapis lazuli, &c. fixes his tools in the lathe, and holds the precious stone to them, thus forming vases, or any other shape, by interposing diamond dust mixed with oil, or emery and water, between the tool and the substance, as often as it is dis- persed by the rotary motion of the for- mer.
The engraving of armorial bearings, single figures, devices, &c. on any of the above stones, after they are polished, is performed through the means of a small iron wheel, the ends of the axis of vfhich are received within two pieces of iron, in a perpendicular position, that may be closed, or otherwise, as the ope- ration requires ; the tools are fixed to one end of the axis, and screwed firm ; the stone to be engraved is then held to the tool, the wheel set in motion by the foot, and the figure gradually formed. The materials of which the tools are made is generally iron, and sometimes brass ; they are flat, like chissels, gouges, ferules, and others have circular heads. After the work is finished, the polishing is done with hair brushes, fixed on wheels and tripoli.
Engraving in wood, has been practised for several centuries, and originally with tolerable success ; it languished for great part of the 18th century, but revived to- wards the close, and is still practised in a manner which reflects credit on the in- genuity of the age. Bewick will long be remembered by his works in this style of engraving, and his imitators have been numerous and successful. As it is entirely different from engrav- ing on copper, the artist already ac- quainted with that mode would find himself at a loss how to proceed on wood, as the lines, instead of being cut into the substance, are raised, like the letters of printing types, and print- ed in the same manner.
The wood used for this purpose is box, which is preferred for the hardness and closeness of its texture ; the surface must be planed smooth, and the design drawn on it with a black lead pencil ; the gra- ver is then used, the finer excavations from which are intended for white in- terstices between the black lines pro- duced by leaving the box untouched, and the greatest lights are made by cut- ting away the wood entirely, of the in- tended form, length and breadth ; but the deepest shades require no engraving. Much of the beauty of this kind of en- graving depends upon the printing, nor
is it every artist who can excel in it, as expedition and freedom are not to be attained : in short, the best wooden cuts are evidently the products rather of per- se verance and ingenuity than easy con- fidence in ability, observable in every line of fine etchings. There are some who succeed to admiration in represent- ing foliage and plants, but unfortunately a few months practice will enub'e a pu- pil to etch them on copper with greater truth : drapery and architecture ;tiuy be well done in wood, but the faces and limbs of figures never look well.
Such are cue diii'erent descriptions of engraving which do not require the aid of aquafortis ; of tho^e made by tb.. in- tervention of that liquid, the principal is Etching. He that would excel in this branch of the arts must be thoroughly acquainted with drawing-; otherwise his works will appear tasteless indeed. The ground used in etching is a combina- tion of asphaltum, gum mastic, and vir- gin wax, mixed in such proportions as will prevent the asphaltum from break- ing the composition, when under the aqua fortis. or the wax from making it so soft as to close the lines when cut through it by the needle. As every thing depends upon the stability of the ground, it should be purchased of those persons who are most celebrated for making it ; or if the person wishing to use it prefers doing it himself, let him remember, that he must keep every par- ticle of grease or oil far from him and his materials, and that, without the great- est care, the inflammability of the as- phaltum will ruin his operations in melt- ing them. The proportions of the ingre- dients should be obtained by experi- ment.
After being prepared in the above man- ner, the ground is tied in a piece of lust- ring for use, and another piece of the same kind of silk must be made into a dabber by tying a quantity of cotton in it. The copper-plate, hammered to a con- siderable degree of hardness, polished as if intended for the graver, and perfectly cleansed with whiting, is then secured at one corner by a hand vice, heated over a charcoal fire, and the silk containing the ground rubbed over it, till every part is covered by the melted composition ; but before it cools the silk dabber must be ap- plied in all directions, till the surface of the plate is thinly and equally varnished. After this part of the process is complet- ed, several lengths of wax taper, twisted together, are to be lighted, the plate rais-
ENGRAVING.
cu by the vice in the left hand, and the right, holding the burning taper,£s to be moved gently backwards and forwards under the ground, carefully avoiding touching it with the wick, yet causing the flame to spread over the surface, which will render it perfectly black, smooth, and shining, in a short time ; this is to be ascertained by turning the plate : If the copper appears through the ground, the taper must be applied again imme- diately ; but if it is held too long beneath the plate, the ground will become opaque, andbivak when the aqua fortis is used.
The next object is, to transfer the de- sign to the ground, which may be done by drawing il on thin white paper with a black-lead pencil, and having it passed through the copper-plate printer's rolling press, who will accomplish it by laying the plate carefully on the board of his press, the pencilled paper slightly damp- ed on it, and turning the press, the lead will be conveyed fi:iniy to the ground, which will appear in perfect outlines on removing the paper. Another method is, to draw the design reversed from the original; rub the back with powdered white chalk, and laying it on the ground, trace the lines through with a blunt point: this operation requires much precaution, or the point will cut the ground; besides, if the paper is not securely fastened with wax at the corners, it may slip, and either interrupt the true continuation of the lines, or scratch the ground.
In working with the etching needle nothing more is required than to keep it upright, that the lines made by it through the ground may not slope, and thus make the aqua fortis corrode improperly ; but it should be particularly observed, that the point, though taper, must be so round- ed as to be free from a possibility of its tearing the surface of the copper, which would prevent the progress of the point, and ruin the plate when bitten ; the ne- cessary polish of the point may be ac- complished by rubbing it on the sole of u shoe. The young artist must now be left to his own exertions, as directions for etching beyond those already given are useless, and he will acquire more knowledge and freedom from copying good prints in one week than a quarto volume of observations would afford. It seems almost needless to add, that every line must be kept distinct, at all events, throughout the plate, and that the most distant should be closer and more regular than those in the fore ground, as the
greater the depth of shade the broader and deeper must the lines be made.
When the etching of the plate is com- pletely finished, the edges of it must be surrounded by a high border of wax, so well secured that water will not penetrate between the plate and it The best spirits of nitre fortis must then be diluted with water, in the proportion of one part of the former to four of the latter, which will be found to answer the first opera- tions, if the weather is fine and the atmo- sphere free from moisture ; but if the contrary is the case, the spirits of nitre must be increased in proportion to the humidity of the air ; this, when poured on the plate, cannot be too attentively observed, in order to remove the bubbles of fixed air with a feather, and to ascer- tain the time for stopping out the lightest parts; for it must be remembered, the whole secret of biting or corroding any subject consists in the judicious manner in which the depth and breadth of the lines are varied, as by proper manage- ment they may be left scarcely percepti- ble, or increased very considerably. The composition used for the above purpose is turpentine varnish mixed with lamp- black, and diluted so as to be used freely with a camel's hair pencil ; this, applied to the parts of the plate sufficiently cor- roded, will effectually prevent the aqua fortis from touching it again, and the re- mainder proceeds as if no such application had taken place : it will be necessary to strengthen the water as the work be- comes nearer completion, but cautiously, lest the ground should be broken ; and every time the aqua fortis is removed, the plate must be washed with clean water, and gradually dried, otherwise the varnish cannot be used, and the lines would be clogged with the decomposed metal. For taking the ground from the plate it is usual to cover the surface with olive oil, and heating it, wipe the plate with a soft piece of old linen and spirits of turpen- tine, will effectually remove all remain- ing dirt.
Re-biting, is the art of strengthening those lines of an etching, in a plate from which the original ground has been cleans- ed. This is done by applying the ground as at first directed, but with great care, that the melted composition does not fill, or even partially fill the lines, to prevent which the cotton wrapt in silk, called the dab ber, should be used exclusively, by taking a small quantity of melted ground on it, and gently touching the parts be-
ENGRAVING.
tween the lines, till they are equally and completely covered ; if the plate is con- siderably heated, the ground \yill spread with more facility over the various inter- rupted surfaces. Carelessness or inatten- tion will instantly ruin this process, and the whole of the plate : a border of wax must surround the parts to be re-bitten, and a channel made to carry off the aqua fortis without injuring those already com- pleted. Supposing the operations of etch- ing and biting the plate entirely finished, nothing more remains than to examine it attentively, and improve it with the graver and dry point.
Stipling, or engraving in the dotted manner, was in a great measure intro- duced by Bartolozzi, whose works in this way are astonishingly numerous, exclusive of those to which his name is affixed, and not the products of himself. Some pasto- ral scenes, with figures, when printed in colours, have a pleasing effect ; and small portraits stipled will bear examination ; but historical subjects, which have great breadth of shade,A appear to no advantage engraved in this manner. Stipling is per- formed by etching the plate with dots, and biting it, laying the shades with a tool for the purpose, using the graver and the dry point, and scraping off the rough- ness thus occasioned.
Engraving in Jlquatinta. The print from an aquatinted plate resembles a neatly finished drawing in Indian ink; this effect is produced by corroding the plate between the particles of a material entirely different from tfee etching ground. The first step in this process is, to prepare a plate exactly in the way already de- scribed, and etch the outlines of the sub- ject to be aquatinted, which are to be slightly bitten, and the plate thoroughly cleansed. The substance used to form the grains of the subject (which may be common resin, burgundy-pitch, asphal- tum, gum-mastich, or gum-copal, either separate or mixed) should be reduced to a fine powder and sifted, put into a piece of muslin, and holding it high above the plate, it must be struck against any sub- stance held in the left hand, till the show- er of dust thus produced has covered the plate equally throughout ; preserving it carefully in this situation, the plate is to be heated sufficiently to melt the powder, which will make the grains as- sume a circular form, and contract, leaving, when cold, a beautiful surface fit for the aqua fortis. Common resin is generally preferred for this part of the operation, but gum-copal is less lia-
ble to be broken loose from the plate during the process of biting.
The drawing to be copied must serve as the future basis of proceeding, which is to be imitated in the following manner , the perfectly white parts of the intended print are to be covered on the plate with the varnish mentioned in etching, by the use of a camel's-hair pencil , a border of wax must then be raised, and the aqua fortis, diluted, poured on ; the same me- thod is afterwards practised in the stop- ping out before recommended, except that the depth of the corroding cannot be so great as in the line manner.
In order to obviate any difficulties which occur in procuringsufficient depths of shade, a method has been invented, that enables the artist to produce an ef- fect almost equal to the decisive touches of a brush filled with colour in drawing, which is the use of a liquid made with water, treacle, or sugar, and fine washed whiting, exactly of the consistence of In- dian ink, and laid on the granulated sur- face with a pencil, in the same free man- ner adopted on paper; after the above composition is thoroughly dry, the whole plate must be covered with a thin, weak, varnish of mastich, turpentine, or asphal- tum, and, when dried a second time, the aqua fortis is to be applied, which imme- diately breaking the varnish and whiting, will corrode the plate precisely in the marks of the pencil. The border of wax may be removed by heating the plate gently, and the ground varnish, &c. by oil of turpentine ; a little fine whiting and a clean rag will then render the plate fit for the printer.
As the manner of procuring the grain by heating the powdered substance scattered over the plate is liable to ob- jections, on account of the difficulty of making the particles assume the desired coarseness, or the reverse, and the en- graving so produced rapidly wearing out in the printing, another has been con- trived, far more certain and satisfactory. In this mode, common resin, mastich, or Burgundy pitch, is dissolved in highly rectified spirits of wine of the best quali- ty, each of which produces different descriptions of grains ; but these sub • stances may be mixed in such propor- tions as the artist prefers, and he must re- collect that the resin makes the coarsest ; to satisfy himself in this prrticular, the grain of every proportion should be tried on useless pieces of copper. Having a solution to his mind, it must remain un- disturbed till every impure particle has
ENG
ENS
subsided. The plate, polished and cleans- ed with whiting1, is then placed to re- ceive the liquid, which being poured on it, is held slanting till the most fluid parts have run off; it is afterwards laid to dry, in the progress of which the resin gra- nulates, and adheres firmly to the surface. The greatest precaution must be used in going through this process, as the in- terposition of dust, grease, hairs, or fi- bres of linen, will cause total derange- ment ; and even then it is subject to most vexatious uncertainty, often compelling the experienced artist to renew it to ob- tain a good grain; in short, ihe weather and untoward accidents frequently ruin his labours, though guarded against by every method his invention suggests. There is one advantage attending the pouring the liquid oft', which is, that the heaviest particles of the resin will float to the lower side, and consequently leave a coarser grain there than above, much better suited to the deep shades of a landscape than if the granulations had been equally fine ; in large subjects the grain is sooietimes laid coarse purposely in the parts requiring it.
Although a fine grain has a very pleas- ing- effect, ami will bear close examina- tion, it has several disadvantages ; for this reason a medium description of gra- nulation is preferable, which, admitting the aqua fortis freely to the copper, it bites deeper, and is less apt by acting la- terally to force off the resin ; besides, the plate will of course afford a greater num- ber of impressions.
Some hints have been given already for biting the plate ; but however useful those may be found in particular instan- ces, there are others which can only be extracted from close application and ex- periment, and those are often varied in their results: as an illustration, we may suppose an artist provided with several pieces of copper granulated, and trying each successively by his watch with spi- rits of nitre diluted to the state of the air at the commencement of his operations, how many minutes are necessary to pro- duce one tint, how many for a second, &c. granting him two hours for his ex- periment ; during this interval a violent shower of rain may occur, which will im- mediately affect the acid, by weakening its properties in the same proportion as salt is observed to be dissolved by a hu- mid atmosphere : thus it appears, a result obtained on a clear dry day will not suit a rainy one, and vice versa.
In opposition to this discouraging un-
certainty, and in opposition to the judg- ment and preference of all true' con- noisseurs, aquatinted prints seem to in- crease in value in the estimation of many persons, who forget that national taste should be improved by works of superi- or execution, and not vitiated by being constantly familiarized to those produced by means which set genius at defiance.
ENNEAGON, in geometry, a polygon with nine sides. If each side be 1, the area will be 6, 18, &c.
ENNEANDRIA, the name of the ninth class in Linnaeus's sexual system, consist- ing of plants which have hermaphrodite flowers, with nine stamina or male or- gans. The orders, or secondary divisions in this class, are three, bein^y founded on the number of the styles, seed buds, or female organs. Laurus tinus, and cassytha, have one style ; rhubarb, (rhe- um,) has a triple stigma or summit, but scarce any style ; flowering rush has six styles. The genera just enumerated are all that belong to the class Enneandria. The first genus, laurus, is very extensive ; comprehending the bay tree, cinnamon tree, camphor tree, benjamin tree, sas- safras tree, and the avocado or avogato pear.
ENS martis, an old name given by chemists to sal ammoniac sublimed with iron filings, and therefore consisting of muriate of ammonia mixed with a little muriate of iron.
Exs veneris, a similar preparation, in which copper filings are substituted for those of iron.
ENSATJE, (from enses, a sword,) the name of the sixth order in Linnaeus's Fragments of a Natural Method, con- sisting of plants with sword-shaped leaves.
ENSIFORM, in general, something- resembling a sword, ensis : thus we find mention of ensiform leaves, ensiform car- tilage, 8cc.
ENSIGN, in the military art, a banner under which the soldiers are ranged, ac- cording to the different companies or places they belong to. The European ensigns are pieces of taffety with various figures, arms, and devices, painted on them in different colours: the Turkish ensigns are horses' tails.
ExstGN is also the officer that carries the colours, being the lowest commis- sioned officer in a company of foot, subor- dinate to the captain and lieutenant It is a very honourable and proper post for a young gentleman on his first coming m- to the army ; he is to carry the colours,
ENT
ENT
both in assault, day of battle, 8cc. and should noi quit th.mbut with his life; he is always to cany them himself on his left shoulder, only on a march he may have them carried by a soldier. If the ensign is killed, then the captain is to carry the colours in his siead.
ENTABLATURE, in architecture, is that part of an order which rests on the capital of a column, and comprehends the architrave, frieze and cornice.
ENTAIL, in liw, signifies fee-tail, or fee in'ailed. See ESTATE.
ENTIBRTIE denotes the whole, in contradistinction to moiety, which de- notes the half; and a bond, damages, &c. are said to be entire, when they cannot be apportioned.
ENTIRE tenancy, signifies a sole pos- session ID one nun.
ENTOMOLOGY is that branch of na- tural nistory that treats of insects. The study of insects has sometimes been ri- diculed as unworthy the attention of men of science ; for this, however, there is no just reason ; though inferior in point of magnitude, yet tiny surpass, in variety of structure and singularity of appearance, all the larger branches of the animal world. No one can examine with an at- tentive eye the subjects of this branch of science without surprise; the great va- riety of forms, the nice adaptation of their parts to the situation in which e.-ich happens to be placed, may excite the amazement of the curious and intelligent mind The same power and wisdom which are manifested in the order, har- mony, and beauty of the heavenly bodies, are equally shown in the formal ion of the minutest insect , each h is received that mechanism of body, those peculiar in- stincts, and is made to undergo those dif- ferent changes, which fit it for its destin- ed situation, and enable it to perform its proper functions. The utility of man\ in- sects, either in their living or dead stat- , as the bee, the crab, the silk worm, co- chineal insect, (see APIS, Coccus, &c.) renders them interesting and import. .nt ; besides tho* diminutive in point of size, they are, in regard to numbers, unques- tionably the most distinguished of the works of nature ; they are to be found in every situation, in water, in air, and in the bowels of the earth ; they live in wood, upon animals, decayed vegetables, and all kinds of flesh, and in every state of its existence down to the most putrid.
The general characters by which in- sects are distinguished are the following : they are furnished with six or more feet ; VOL. V.
the muscles are affixed to the internal surface of the skin, which is a substance more or less strong, and sometimes very hard and horny ; they do not breathe like larger animals, by lungs or gills situated in the upper part of the body ; but by a sort of spiracles distributed in a series or row 'on each side the whole length of the abdomen ; tin se are supposed to commu- nicate with a continued chain, as it were, of lungs, or something analogous to the- m, distributed throughout the whole length of the body; the head isfurnisned with a pair of what are termed antennae, or horns, which are extremely different in different tribes, and which by their struc- ture, &c. form a leading character in the institution of the genera into which in- sects are divided
Writers on natural history formerly in- cluded snails, worms, and the smaller ani- mals, or animalcules, in general, among insects: these are now more properly placed among the tribe vermes, or worm- like animals Late writers have extend- ed this still further, and have very pro- perly excluded almost the entire Linnaean order of Aptera. forming of it a distinct class, under the name of Crustacea. In- sects have also been denominated blood- less animals, which modern discoveries have shewn to be contrary to fact : iiieir blood is generally a colourless sanies. Some of them, as the cimex lectularius, have been frequently used, with the mi- croscope, to exhibit in a striking marine? the circulation of the blood. In this in- sect, with a good glass, the vibrations and contractions of the arteries may be distinctly observed.
Most insects are oviparous; of course, the first state in which insects appear is that of an ovum or egg. This relates to the generality of insects, for there ;u-e some examples of viviparous insec's, as in the genera Aphis, Musca, &c. From the egg is hatched the insect in i's second or caterpillar state ; this second state lias been usually known by the name of eruca, but Linnaeus has changed it to that of LARVA, which see ; considering it as a sort of masked form, or disguise, of the insect in its complete state. The larvae of insects differ very much from each other, according to the several tribes to which they belong : those of the butterfly and moth tribe (phalaena) are generally known by the name of caterpillars ; those of the beetle (scarabaeus,) except such as inhabit the water, are of a. thick, clumsy form. The larvae of the locust, or grass- hopper, (gryllus,) do not differ very E
ENTOMOLOGY.
much in appearance from the complete insect, except being without wings. The larvae of flies, bees, (musca, apis,) &c. are generally known by the name of mag- gots, and are of thick short form. Those of water beetles (dytiscus) are of highly singular forms, and differ, perhaps, more from that of the complete insect than any others, except those of the butterfly tribe. Some insects undergo no change of shape, but are hatched from the egg complete in all their parts, and they undergo no farther alteration than that of casting their skin from time to time, till they ac- quire the complete resemblance of the parent animal. In the larvae state most insects are peculiarly voracious, as in many of the common caterpillars. In their perfect state some insects, as butterflies, are satisfied with the lightest nutriment, while others devour animal and vegetable substances with a considerable degree of avidity. When the larva is about to change into the crysalis or pupa state, it ceases to feed, and having placed itself in some quiet situation, lies still for several hor.rs, and then, by a sort of effort, it di- vesis itself of its external skin, and imme- diauly appears in the different form of a chrysalis or pupa ; in this state, likewise, the insects of different genera differ al- most as much as the larva. In most of the beetle tribe it is furnished with short legs, capable of some degree of motion, though very rarely exerted. In the but- terfly tribe it is destitute of legs ; but. in the locust tribe it differs very little from the perfect insect, except in not having the wings complete. In most of the fly tribe it is perfectly oval, without any ap- parent motion or distinction of parts The pupa of the bet is not so shapeless as that of flies, exhibiting the faint appearance of limbs. Those of the dragon-fly (libellula) differ most widely from the appearance of the complete insect ; from the pupa emerges the insect in its ultimate form, from which it never changes, nor re- ceives any farther increase of growth.
Different naturalists have attempted to arrange insects into families and gene- ra, particularly the celebrated Linnaeus, whose arrangement may be thus explain- ed. He has formed them into seven families or orders, composing his sixth class of animals, Insecta : he defines an insect, a small animal, breathing through pores on its sides, furnished with movea- ble antennae and many feet, covered with either a hard crust or a hairy skin. As in- troductory to the distinguishing marks of the orders and genera, it will be ne-
cessary to enumerate and explain the terms given to the different parts, and the most remaikuble of the epithets applied to them by entomologists. The body is divided into head, trunk, abdomen, arid extremities.
1. Caput, the head, is in insects, as well as in the vertebral animals, the principal repository of the senses, and contains that most important organ, the brain : externally it is furnished with eyes ; stem- mata ; antennae ; clypeus ; vertex ; mouth; front ; gula.
Eyes, are situated on each side of the head, and differ much in form and colour in the different insects, and may be con- sidered amongst the most surprising of nature's works ; they are not, us might be at first supposed, mere hemispherical bodies of plane and simple surfaces, but examination proves them to be composed of an immense assemblage of highly wrought hexagonal fascets, each furnish- ed with its proper optic nerve, retina, 8tc. complete for vision : the number of these fascets differs in different species ; in the eye of the common fly 8,000 have been counted, and in that of the libellula or dragon fly about 12,000.
Stemmata are hemispherical bodies placed upon the vertex, and are suppos- ed to perform the office of eyes. The antennae are two articulated moveable processes, placed on the head ; they are either, 1. Setacea, setaceous, i, e. like a bristle, when they taper gradually from their base to their point. 2. Clavatae, cla- vated, i.e. club-shaped, when they grow gradually thicker from their base to their point. 3. Filiformes, filiform, i. e. thread- shaped, when they are of an equal thick- ness throughout the whole of their length. 4. Momlitbrmes, moniliform, ». e. of the form of a necklace, when they are of an equal thickness throughout, but formed of a series of knobs, resembling a string of beads. 5. Capitatae, capitate, when they grow thicker towards the point, and terminate in a knob or head. 6. Fis- siles, fissile, i. e. cleft, when they are capi- tate, and have the hea<l or knob divided longitudinally into three or four parts or laminae. 7. Perfoliatae, perforated, when the bead or knob is divided horizontally. 8. Pectinatae, pectinated, i. e. resembling a comb, when they have a longitudinal series of hairs projecting from them, in form of a comb. 9. Barbatae, barbed, when they have little projections or barbs placed on their sides : they are either longiores, longer than the body; bre- viores, shorter than the body ; or, me*-
ENTOMOLOGY.
diocres, of the same length with the bo.ij
Cv vier has shewn that the organs of hearing are placed at the base of the antennae i:* the Crustacea, such as crabs and lobsters, and from analogy many na- turalists have supposed them to be simi- larly situated in the true insects; this may probably be correct, but it has not yet been proved, and must not therefore be assumed.
Clypeus, the covering of the head in the beetle tribe ; it extends from the eyes, often projecting over the mouth.
Vertex, the top of the head above the front.
Front, this term is applied to the an- terior part of the head of most insects, and is analogous to the clypeus of the beetles.
Gula, throat, underneath the head, sup- porting the lip.
Mouth, is situated in the head, rarely in the breast, and affords so great a' variety of characters, that the celebrated Fabricius founded upon them his entire system of arrangement ; the principal and most obvious parts are, the palpii, mandi- bulae, labrum, labium, ligula, maxillae, and galeae.
Palpi, or feelers, are articulated fila- ments of different forms, sometimes re- sembling antennae, placed in the mouth, either on the jaws or lip ; they are two, or four, or six, in number, and are either anterior, intermediate, or posterior, or, according to Latreille, labial or maxillary. Considered in relation to those parts upon which they are situated, they generally furnish good generic characters.
Mandibulae, mandibles, two horny curv- ed pieces, placed one on each side of the mouth, moving laterally, and used by the insect either to seize its food, or as" wea- pons in its combats.
Maxillae, jaws, two horny or submem- branaceous pieces, placed one under each mandible, generally ciliated with hair, or dentate on the inner side, and always pal- pigerous in those insects that have more than one pair of palpi.
Labrum, or as it is sometimes termed labium superius, upper lip, a transverse moveable piece, placed immediately be- low or underneath the clypeus and above 'he mandibles.
Labium, lip, termed by some entymo- logists labium inferius, and by others mentum, or chin, a horny substance, sometimes truncate, and terminates the mouth ; beneath it supports the posterior palpi, and serves as a sheath for the *ongue.
Ligula, a soft instrument, coriaceous at the base, often bifid at the tip, and re- tractile ; this part is found only in insects provided with mandibles.
Galas, casque, two membranaceous, in- articulate pieces, placed one on each side of the mouth in some insects of the hemiptera and neuroptera orders, and in conjunction with the lips covering the mouth ; this part is by some considered as an anterior palpi, or an exterior divi- sion of the jaws.
In some insects the mouth is elongated into a tube, or placed at the end of a pro- jection of the head, and is then either a lingua, proboscis, haustellum, rostellum, or rostrum.
Lingua, tongue, soft, flexible, tubular, involuted, like the spring of a watch, usually obtuse at its termination, and placed under the head between the palpi of the butterflies and moths.
Proboscis, trunk, soft, retractile, inar- ticulate, labiated at the extremity, and is peculiar to the flies ; the common fly af- fords a good example of it.
Haustellum, sucker, composed of very fine and rigid filaments, enclosed in a bivalve sheath, and is peculiar to the cimices, and some of the flies.
Rostellum, a bill, or beak, coriaceous, articulate, and inclosing the haustellum.
Kostrum, a prolongation of the head, terminated by the mouth, as in the cur- cuhos, &c.
Some of these terms are not used by some authors as here defined ; and in- deed so unsettled are many entomologi- cal terms, that the student is often very much perplexed by the various applica- tions of them.
II. Truncus, the trunk, to which the legs are attached, is situated between the head and the abdomen ; it is divided into, 1. The thorax, or chest, which is the superior part. 2. Scutellum, i. e. small shield or escutcheon, separated from it by a suture, on the posterior part. 3. The breast and sternum, which is the in- ferior part.
III. The abdomen, that part which con- tains the stomach, intestines, and other viscera, consists of several annular seg- ments ; it is perforated on the sides with spiracula, or breathing-holes ; the upper part of it is termed tergum, or back ; the inferior part venter, or belly ; the pos- terior part anus.
IV. Artus, the extremities, are the wings, legs, and tail.
(1.) Ate, the wings, are two or four ; they are either, J , Plan^e, *. e. plain, swell
ENTOMOLOGY.
as cannot be folded up by the insect : or, 2. PJkatiies, or folding, such as can be foli led up by the insect at pleasure. 3. Er. ctze, erect, such as have their superior surfaces brought into contact, and stand upright when the insect is at rest. 4. Pat'entes, spreading ; such as are extend- ed horizontally. 5. Incumbentes, incum- bent ; such as rest on the upper part of the abdomen 6. DeHexae, bent down ; such as are partly incumbent, but have their exterior edge inclined towards the sides of the abdomen 7. Reverse, re- versed ; such as are incumbent, but in- verted. 8. Dentatae, such as have their edges notched or serrated. 9. Caudatae, such as have processes extended from their extremities like a tail. 10. Reticu- lalae, netted; when the vessels of the wiisgs put on the appearance of net-work. 11 Pictx, puinred; such as are marked with coloured spots, bands, streaks, lines, or dots. 12. Notatae, marked with specks. 13. Ornatae, adorrud with little eves, Or circular spots, containing a spot of a dif- ferent colour in their centre : the central spot is termed pupil; the exterior one is called iris; this may happen either in the primary or secondary wings, on their up- per or under surfaces : the superior wing is called primary, and the inferior secon- dary, to avoid confusion, as they may be at times reversed. The elytra are hard shells, occupying the place of the upper wings. They are for the most part move- able, and are either, 1 Trnncata, trun- cated, when shorter than the abdomen, and terminated by a transverse line. 2. Spinosa, or prickly, when their surfaces are covered with sharp points or prickles. 3. Serrata, serrated, when their edges are notched. 4. Scabra, rough, when their surface resembles a file. 5. Striata, striated, when marked with slender lon- gitudinal furrows. 6. Porcata, ridged, when marked with elevated ridges. 7. Sulcata, furrowed. 8. Punctata, marked with dots. 9. Fastigiata, when formed like the roof of a house. The hemelytra, as it were half-elytra, partaking partly of the nature of crustaceous shells, and membranaceotis wings, being formed of an intermediate substance. Halteres, or poisers, are small orbicular bodies placed on stalks, situated under the wings of in- sects, of the order Diptera.
(11.) Pedes, the legs, are divided into, 1. Femur, or thigh, that part which is joined to the trunk. 2. Tibia, or shank. 3. Tarsus, or foot. 4. Ungues, hooks or nails. 5. Manus, (chela,) hands or claws, simple, with a moveable thumb, as in the crab, The hind legs are termed, 1.
Cursorii, formed for running. 2. Salta- ton., formed ibr leaping 3. Nat»torii, formed for swimming.
(Ill.)Cauda, the tail, which terminates the abdomen, is 1. Solitaria, i. e. single.
2. Bicornis, i. e. two-horned, or double.
3. Simplex, simple, i. e. unarmed. 4,. Armata, i. e. furnished : 1. with forceps or pincers : 2. with furca, a fork : 3. with one or more setae, or bristles : 4 with an aculeus, or sting, either smooth or barb- ed. A sting is a weapon frequently hol- low, with which some insects are furnish- ed, and through which they discharge a poison into the wound they inflict.
The sexes of insects are commonly two, male and female. Neuters are to be met with among those insects which live in swarms, such as ants, bees, &c.
The majority of insects are observed to be annual, finishing the whole term of their lives in the space of a year or less, and man} do not live half that time ; na\ , there are some which do not sur- vive many hours ; but this latter period is to be understood only of the animals when in their complete or ultimate form, for tne larvae of such as are of this short duration have in reality lived u very long tune under water, of which they are na- tives ; and it is observed, that water in- sects, in general, are of longer duration than land insects. Some few insects, however, in their complete stale, are supposed to live a considerable time, as bees for instance ; and it is well known that some of the butterfly tribe, though the major part perish' before winter, will yet survive that season in a state of tor- pidity, and again appear and fly abroad in the succeeding spring; spiders :.re also thought to live a considerable time, and some species of the genus cancer are said to live several years, especially the common lobster, &c. : it should be observed, however, that these animsls, in the opinion of some modern naturalists, constitute a different tribe of beings from insects properly so called. Linnaeus has divided insects into seven orders 1. Co« LEOPTEUA ; II. HEMUPTEHA ; 111 LEPIDOP- TERA ; IV. NEUROPTEUA; V. HYMEXOP- TEHA; VI. DU-IERA; VII. APTERA, which see : and from these the several genera are referred to.
ENTRY, in law, is the taking possession of lands or tenements, where the party has a title of entry, or an immediate right to possess them. This may be in person, or by attorney, or is an entry in law, which is merely the making con-
ENT
ENV
tinual claim, by law considered equiva- lent to entry. A right of entry is when a party may have his remedy, either by entering1 into the lands, or by action to recover it. A title of entry is where one has a lawful entry in the land which ano- ther has, but has no action to recover it till he has entered.
Entry is a summary remedy against certain species of injury by ouster, or putting1 out of possession of lands; when the party must rmke a formal but peace- able entry, declaring that he takes pos- session ; or may enter upon any part in the same county in the name of the whole ; and if he cannot go upon the land for bodily fear, he may make a claim as near the estate as he can, which must be repeated once within every year and clay, and is culled continual claim. This remedy is admitted only where the adverse possession originally commenced by wrong, as in the in- stances technically called abatement, in- trusion, or disseisin. On a discontinuance or deforcement, the party is put to his action. Even in the former cases, when the original wrongful possessor dies, and the land comes to his heir, the right of entry is tolled, i. e. taken away by the descent. If the claimant was under dis- ability, from age, coverture, 8tc. the en- try is not tolled by descent ; nor in case of an actual disseisin, unless the disseisor was in peaceable possession for five years. Stat. 32 Henry VIII. c. 33. En- try must be made within 20 years after the claimant's right shall accrue, 21 Jac.
I. c. 16 ; and by 4 and 5 Anne, c. 16, no entry shall avail to save this statute, un- less an action is commenced and prose- cuted with effect upon it within one year after ; and, finally, by stat. 5 Ric.
II. st. 1. c. 8j entry must be pursued in a peaceable manner ; for if one turns or keeps another out of possession forcibly, it is not only the subject of a civil reme- dy, but of a fine and punishment for a misdemeanor.
E N i RI , the writ of, is a possessory re- medy, which disproves the title of the tenant or possessor, by shewing the un- lawful rrnans by which he entered or continues in possession. It was former- ly an usual mode of recovering lands, but is now disused for the more conve- nient action of ejectment, and is never brought when that remedy can be used. There is much nice technical learning concerning it, which it would be vain to attempt to a'-s ridge in a popular work. It derives different denominations from
the different cases to which the writ ia applied, and those are generally derived from the terms in which it states the wrongful entry to have been made, or sets out the different degrees of descent, through which the lands have passed in the possession of the wrongful tenants. After a certain degree of descents, these are no longer noticed in the writ. The writ against the immediate wrong doer is called a writ of entry in nature of as- size : that upon one descent, an entry sur disseisin in the per,- and upon an en- try where the first disseisor has enfeoffed another, and he a third, it is an entry sur disseisin in le per et eni. An entry in le post states only that the tenant hath not entry but after (post) the disseisin of A. B. which is allowed in cases beyond the foregoing degrees. There are other writs adapted to particular cases, which we shall only mention by name, and re- fer to the larger dictionaries of the law for their precise meaning : such are
EXTHY ad commwiem legem, for the re- versioner of tenants in dower by cour- tesy for life, &c.
ENTRY ad terminurn qui protteriit, a writ for the reversioner, after the end of a term or estate for life, against a stranger in possession.
ENTRY in casu consimili.
ENTRY in casu proviso.
EVTIIY causa matrimonii prcelocuti.
Several points of law occur, as to the effect of an entry in the case of joint tenancy and coparcenary ; of entry by the heir ; of entry to divest an estate ; to take advantage of a condition which cannot be investigated here; but in ge- neral it may be observed, that a bare en- try, without expulsion, makes only a seisin ; so that the law thereupon ad- judges him in possession who has the right.
ENVELOPE, in fortification, a work of earth, sometimes in form of a simple parapet, and at others like a small ram- part with a parapet : it is raised some- times on the ditch, and sometimes be* yond it.
EXVOY, a person deputed to nego- tiate some ,-ffair with any foreign prince or state. Those sent from the courts of France, Britain, Spain, &c. to am petty prince or state, such as the princes of Germany, the republics of Venice, Ge- noa, &c. go in quality of envoys, not ambassadors, and such a character only do those persons bear, who go from any of 'he principal courts of Europe to another, when the affair they go upon is
EPA
EPA
not very solemn or important. There are envoys ordinary and extraordinary, as well as embassadors ; thu\ arc equally the same under the protection of the law of nations, and enjoy all the privi- leges of embassadors, only differing from them in this, that thr same ceremonies are not performed to them.
ENURE, in law, to take place or ef- fect, or be available, as a release made to a tenant for a term of life shall enure to him in the reversion.
EPACRIS, in botany, a genus of the PfiitHiidria Monogvnia class and order. Calyx five-parted ;' corolla funnel-form, villous ; nectariferous scales, growing to the germ ; capsule five-celled, five-valv- ed ; the partitions from the middle of the valves ; sei-ds minute and numerous. There are four species, natives of New Zealand.
EPACT, a number arising from the excess of the common solar year above the lunar, whereby the age of the moon may be found out every year. See CHRONOLOGY. The excess of the solar year above the lunar is 11 days ; or the epact of any year expresses the num- ber of days from the last new moon of the old year, which was the beginning of the present lunar year, to the first of January. The first year of the cycle of the moon, the epact is 0, because the lunar year begins with the solar. On the second, the lunar year has begun 11 days before the solar year, therefore the epnct is 11. On the third, it has begun twice 11 before the solar year, therefore the epact is 22. On the fourth, it begins three times 11 days sooner than the solar year, the epact would therefore be 33 ; but 30 days, being a synodical month, must that year be intercalated ; or that year must be reckoned to consist of thirteen synodical months, and there re- mains three, which is the true epact of the year; and so on to the end of the cycle, adding 11 to the epact of the last year, and always rejecting 30, gives the epact of the present year. Thus, to ad- just the lunar year to the solar through the whole of 19 years, 12 of them must consist of 12 synodical months each, and 7 of 13, by adding a month of 30 days to every year when' the epact would exceed 30, and a month of 29 days to the last year of the cycle, which makes in all 209 days, i. e."l9xll; so that the inter- calary or embolimaean years in this cycle are 4, 7, 10, 12, 15, 18, 19.
If the new moons returned exactly at the same time after the expiration of
nineteen years, as the council of Nice supposed they would do (when they fix- ed the rule for the observation of Easter, and marked the new moons in the calen- dar for each ye?r of the lunar cycle) then the golden number, multiplied by 11, would always give the epact. But in a Julian century, the new moons antici- pate, or happen earlier, than that coun- cil imagined they would by _8_ of a day. In a Gregorian common century, which is one day shorter than a Julian century, they happen 1.7. of a day la'.er, (1 day — A = W' Novv « X 3 - ji for the three common centuries, but J* oeing subtracted, on account of the Gregorian bissextile century, there will remain 4.3'. Therefore, in four Gregorian centuri -s, the new moons will happen later by .43 of a day, and the epacts must be de- creased accordingly.
At present the "Gregorian epact is 11 days short of the Julian epact ; but the quotient of the number of the centuries divided by 4, which at this time is 4, mul- tiplied by .4.3, with the addition of the re- mainder 1 multiplied by ll, makes in all but l_y>, or 7 days +^4 . therefore |6.t i. e. 3 days -f- 1 £ must be added to com- plete the 11 days. Whence we have the following
General rule for finding the Gregorian Epact Jor ever. Divide the centuries of any year of the Christian sera by 4, (re- jecting the subsequent numbers ; multi- ply the remainder by 17, and to this pro- duct add the quotient multipled by 43 : divide the product -f- 86 by 25 : multiply the golden number by 11, from which subtract the last quotient ; and rejecting the thirties, the remainder will be the epact.
Example for 1808.
18-^-9 = 2
2 x 17 = 34
43 x 4 4- 34 =206
206 -f- 86 -i- 25 = 11
11 X 4 (Gold. No.) = 44
44-11
= 1 — 3 = Epact.
30
Jl shorter ride for finding the epact until the year 1900. Subtract 1 from the gold- en number, and multiplying the remaiir- der by 11, reject the thirties, and you have the epact.
EPM
Example for the year 1808,
Golden Number 4. 4 — Ixll — 30 = 3 = Epact.
EPAULE, in fortification, denotes the shoulder of a bastion, or the place where its face and flank meet, and form the an- gle called the angle of the shoulder. See BASTION.
EPAULEMENT, in fortification, a work raised to cover sideways, is either of earth, gabions, or fascines, loaded with earth. The epaulements of the places of arms for the cavalry, at the entrance of the trenches, are generally of fascines mixed with earth.
EPAULETTES, in military dress, are a sort of shoulder-knot They are badges of distinction worn on one or both shoul- ders, according to the rank of the wearer, and for the same reason they are made either of worsted, or of silver or gold lace. In France, all degrees of rank in the army may be instantly known from the epaulette ; but this is" not the rase here. Lately epaulettes have been intro- duced into the navy, and in that service the following are the gradations of rank as distinguished by them. Masters and commanders have one epaulette on the left shoulder : post captains under three years, one epaulette on the right shoul- der, afterwards two epaulettes : rear ad- mirals have one star on the strap of the epaulette, vice-admirals two stars, and admirals three stars
EPHA, or EPHAH, in Jewish antiquity, a measure for tilings dry, containing 1.0961 of a bushel. See MEASURE.
EPHEDRA, in botany, a genus of the Dioecia Monodelphia class and order. Natural order of Coniferx. Essential character : male, calyx of the ament two- cleft ; corolla none;' stamens seven; an- thers four inferior, three superior : fe- male, calyx two-parted, five-fold: corol- la none ; pistils two ; seeds covered with a berried calyx. There are two species ; viz. E. distachya, great shrubby horse tail, or sea-grape, and E monostachya, small shrubby horse tail. These plants vary extremely. Some in the south of Europe, are only a hand in height, whilst others are three feet : they are found in most of the southern parts of the Russian dominions, from the Volga to the Lena, and southwards to Persia and India. The berries are sweetish, mu- cose, and leave a little heat in the throat : they are eaten by the Russian peasants, and the wandering hordes of all Great Tartary.
EPHEMERA, day-fly, in natural his- tory, a genus of insects of the order Neu- roptera. Mouth without mandibles ; feelers four, very short, filiform; anten- nae short, filiform ; above the eyes are two or three large stemmata ; wing^s erect, the lower ones much shorter ; tail terminating in long bristles or hairs. These short-lived animals, of which there are about twenty species, in two divi- sions, according as they have two or three hairs in the tail, are found every where about waters in the summer, and in their perfect state seldom live more than a day or two, some of them not an hour, during which time they perform all the functions of life, and answer all the ends of nature. The larva lives under water, and is eagerly sought after by trout and other fish: it is six-footed, ac- tive, and furnished with a tail and six la- teral fins or gills ; the pupa resembles the larva, except in having rudiments of future wings. The larva is altogether aquatic, the complete insect aerial. In the former state it livestwo or three years ; but as a perfect animal it survives but a very fuw hours, perishing in the course of the same evening that gives it birth. The most common species in Europe is the E. vulgata, or common May-fly, so plentiful in 'he early part of summer about the brinks of rivulets and stagnant waters. It is of a greenish colour, with transparent wings elegantly mottled with brown, and is furnished with three very long black bristles It flutters in the evening about the surface of the water; but during the day is generally seen in a quiescent posture, with the wings closed, and applied to each other in an upright position,
EPHEMERIDES, in literary history, an appellation given to those books or journals, which shew the motions and places of the planets for every day in the year. It is from the tables contained in these ephemerides, that eclipses, and all the variety of aspects of the planets, are found.
EPHIELIS, in botany, a genus of the Octandria Monogynia class and order. Esential character: calyx five-parted; petals five, with claws ; nectary ten scales, two to each petal ; capsule ob- long, one celled, two-valved, two-seeded. There is but one species; viz. E. guia- nensis : this is a lofty tree growing in the forests of Guiana, where it flowers in the month of October.
EPIBATERIUM, in botany, a genus of the Monoecia Hexandria class and or-
I
EP1
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der. Essential character : calyx double ; outer six-leaved, small ; inner three-leav- ed, large,- petals six, three outer, between the calycine leaflets; three inner ; drupes three, subglobuiar, mucronate, with three permanent styles; inclosing a kidney- form nut. There is only one species; viz. E. pendulum.
EPIC, or heroic poem, a poem express- ed in narration, formed upon a story part- ly real and partly feigned. ; representing1, in a sublime style, some signal and for- tunate action, distinguished by a variety of great events, to form the morals, and affect the mind with the love of heroic virtue.
EPJCHIIYSUM, in botany, a genus of the Cryptogumia Fungi class and order. Fungus rounded, concave ; seeds globu- lar; tailless, attached to a branched thre.id creeping within. Tht-re is but one spe- cies; viz. E. argentt'iim.
EPICURE AN philosophy, the doctrine or system of philosophy maintained by Epicurus and his followers.
Epicurus, the Athenian, one of the greatest philosophers of his age, was obliged to Uemocritus for almost his whole system, notwithstanding he piqued himself upon deriving every thing from his own fund. He wrote a great number of books, which are made to amount to above 300. Though none of them are come down to us, no ancient philoso- pher's s) stem is better known than his, for which we are mostly indebted to the poet Lucretius, D ogenes, JLaertius, and Tolly. His philosophy consisted of three parts, canonical, physical, and ethereal. The first was about the canons, or rules of judging. The censure which Tully passes upon him, for his despising logic, will hold true only with regard to the logic of the Stoics, which he could not approve of, it being too full of nicety and quirk. Epicurus was not acquainted with the analytical method of division and ar- gumentation, nor was he so curious in modes and formal ion, as the Stoics. Soundness and simplicity of sense, assist- ed with some natural reflections, was all his art. His search after truth proceed- ed only by the senses, to the evidence of which he gave so great a certainty, that he considered them as an infallible rule of truth, and termed them the first natural light of mankind.
In the second part of his philosophy he laid down atoms, space, and gravity, as the first principles of all things. He
did not deny the existence of a God, but thought it beneath his majesty to concern himself with hurmn affairs. He held him a blessed immortal being, having no af- fairs of his own to take care of, and above meddling with those of others. See ATO- MIC PHILOSOPHY.
As to his el hies, he made the supreme good of man to consist in pleasure, and, consequently, supreme evil in pain. Na- ture itself, says he, teaches us this truth, and prompts us from our b'nh to procure what ever gives us pleasure, and avoid what gives us pain. To this end he pro- poses a remedy against the sharpness of pain : this was to divt- rt the mind from it, by turning our whole attention upon the pleasures we have formerly enjoyed. He held ihat the wise man must be iiappVi as long as he is wise ; that pain, not depriv- ing him of his wisdom, cannot deprive him of his happiness.
EPICYCLE, in the ancient astronomy, a little circle, whose centre is in the cir- cumference of a greater circle ; or it is a small orb or sphere, which, being fixed in the deferent of a planet, is carried along with it ; and yet, by its own peculiar mo- tion, carries the planet fastened to it round its proper centre.
It was by means of epicycles, that Pto- lemy and his followers solved the various phenomena of the planets, but more espe- cially their stations and retrogradations. The great circle they called the excen- tric or deferent, and along its circumfer- ence the center of the epicycle was con- ceived to move ; carrying with it the planet fixed in its circumference, which in its motion downwards proceeded ac- cording to the order of the signs, but in moving upwards contrary to that order. The highest point of a planet's epicycle they called apogee, and the lowest peri- gee.
EPICYCLOID, in geometry, a curve generated by the revolution of the peri- phery of a circle, ACE (Plate V Mis- eel, fig. 4 ) along the convex or concave side of the periphery of another circle, 1) G B.
The length of any part of the curve, that any given point in the revolving cir- cle has described, from the time it touch- ed the circle it revolved upon, shall be to double the versed sine of half the arch which all that time touched the circle at rest, as the sum of the diameters of the circles to the semidiameter of the rest- ing circle, if the revolving circle moves upon the convex side of the resting cir
EPI
EPI
ele ; but if upon the concave side, as the difference of the diameters to the semi- diameter of the resting circle. , In the Philosoph. Transactions, No. 218, we Lave a general proposition for measuring the areas of all cycloids and epicycloids, viz. The area of any cycloid or epicycloid is to the area of the gene- rating circle, as the sum of double the velocity of the centre and velocity of the circular motion to the velocity of the circular motion : and in the same propor- tion are the areas of segments of those curves to those of analogous segments of the generating circle.
EPIDEMIC. A contagious disease is so termed that attacks many people at the same season, and in the same place ; thus, putrid fever, plague, dysentery, &c. are often epidemic. Dr. James Sims observes, in the Memoirs of the Medical Society of London, that there are some grand classes of epidemics which prevail every year, and which are pro- duced by the various changes of the sea- sons. Thus, spring is accompanied by inflammatory diseases ; summer by com- plaints in the stomach and bowels ; au- tumn by catarrhs; and winter by inter- mittents. These being obviously pro- duced by the state of weather attendant upon them, other epidemics are suppos- ed analogous to them, and obedient to the same rules, which, on examination, not being the case, all further scrutiny is laid aside, perhaps too hastily.
The most natural and healthful seasons in this country are, a moderately frosty winter, showery spring, dry summer, and rainy autumn; and whilst such prevail, the wet part of them is infested by vastly the greatest proportion of complaints, but those not of the most mortal kind. A long succession of wet seasons is accom- panied by a prodigious number of diseases; but these being mild and tedious, the number of deaths are not in proportion to the co-existent ailments. On the other hand, a dry season, in the beginning, is attended with extremely few complaints, the body and mind both seeming invigor- ated by it; if, however, this kind of weather last very long, towards the close of it a number of dangerous complaints spring up, which, as they are very short in their duration, the mortality is much greater than one would readily suppose, from the few persons that are ill at any one time: and as soon as a wet season succeeds a long dry one, a prodigious sickness and mortality come on univers- ally. So long as this wet weather con-
VQL. V.
i
tinues, the sickness scarcely abates, but the mortality diminishes rapidly ; so that in the last number of rainy years the number of deaths is at the minimum. The change of a long dry season, whether hot or cold, to a rainy one, appears to bring about the temperature of air fa- vourable to the production of great epi- demics. Some, however, seem more speedily to succeed the predisposing state of the air, others less so; or it may be, that the state of the air favourable to them exists at the very beginning of the change, whilst the state favourable to others progressively succeeds : of this last, however, Dr. Sims is very uncertain.
Two infectious diseases, it appears, are hardly ever prevalent together ; there- fore, although the same distemperature of air seems favourable to most epidemic disorders, yet some must appear sooner, others later. From observation and books, the Doctor describes the order in which these disorders have a tendency to succeed each other to be, plague, pe- techial fever, putrid sore throat, with or ^without scarlatina, dysentery, small-pox, measles, simple scarlatina, hooping-cough, and catarrh : " I do not mean by this," says he, " that they always succeed each other as above ; for often the individual infection is wanting, when another takes its place, until perhaps that infection is imported from a place, which has been so unfortunate as to have a co-incidence of the two causes, without which it ap- pears that no epidemic can take place : that is, a favourable disposition of the air, and that particular infection. Whenever it happens that one infectious disorder takes the place that should have been more properly occupied by another, it becomes much mom virulent than it is naturally, whilst the former, if it after- wards succeeds, becomes milder in pro- portion : this, perhaps, is the reason why the same disorders, nay, the same ap- pearance in a disorder, are attended with much more fatality in one vear than another."
EPIDENDRUM, in botany, a genus of the Gynandria Diandria class and order. Natural order of Orchidese. Essential character: nectary turbinate, oblique, re- flex ; corolla spreading ; spur none, There are 124 species. This numerous genus is obscure in its character, differ- ences, and synonyms: for the flowers in dried specimens can hardly be unfolded ; the plants are cultivated in gardens with difficulty ; and the species have not been sufficiently described by authors, who
F
EPI
EPI
have had an opportunity of seeing them in America and the East Indies, their na- tive places of growth.
EPIDERMIS, in anatomy, the same with the cuticle. See CUTIS.
EPIGJEA, in botany, a genus of the Decandria Monogynia class and order. Natural order of Bicornes. Ericx, Jus- sieu. Essential character: calyx outer three-leaved ; inner five-parted ; corolla salver-form ; capsule five-celled. There are but two species, liz. E. repens, creep- ing epigsea, or trailing arbutus, and E. cordifolia, heart-leaved epigxa : the form- er, remarkable for its fine odour, is a na- tive of Virginia and Canada, and the latter of Guadaloupe.
EPIGLOTTIS, one of the cartilages of the larynx or wind-pipe. See ANA- TOMY.
EPIGRAM, in poetry, in short poem or composition in verse, treating only of one thing, and ending with some lively, inge- nious, and natural thought or point.
EPILEPSY, in medicine, the same with what is otherwise called the falling sickness, from the patient's falling sud- denly to the ground.
EPILOBIUM, in botany, a genus of the Octandria Monogynia class and or- der. Natural order of Calycanth erase. Onagrse, Jussieu. Essential character : calyx four-cleft; petals four; capsule oblong, inferior ; seeds downy. There are fourteen species. These plants are hardy perennials, not void of beauty ; they are, however, commonly considered only as weeds, and are rarely cultivated in gardens. The American species are, 1. E. estoratum; 2. E. spicatum; 3. E. strictum ; 4. E. linerate.
EPILOGUE, in dramatic poetry, a speech addressed to^he audience after the play is over, by one of the principal actors therein, usually containing some reflections on certain incidents in the play, especially those in the part of the person that speaks it.
EPIMEDIUM, in botany, English bar- remvort, a genus of the Tetrandria Mono- gynia class and order. Natural order of Corydales. Berberides, Jussieu. Essen- tial character : nectary four, cup-form, leaning on the petals ; corolla four petal- led ; calyx very caducous ; fruit a silique. There is but one species, viz. E. alpinum, alpine barrenwort.
EPIPHANY, a Christian festival, other- wise called the manifestation of Christ to the Gentiles, observed on the sixth of Ja- nuary, in honour of the appearance of our Saviour to the three magi, or wise
men, who came to adore him, and bring him presents. The feast of Epiphany was not originally a distinct festival, but made a part of that of the nativity of Christ, which being celebrated twelve days, the first and last of which were high or chief days of solemnity, either of these might properly be called Epiphany, as that word signifies the appearance of Christ in the woi'ld.
The kings of England and Spain offer gold, frankincense, and myrrh, on Epiph- any, or twelfth day, in memory of the offerings of the wise men to the infant Jesus.
The festival of Epiphany is called by the Greeks the feast of lights, because our Saviour is said to have been baptised on this day ; and baptism is by them call- ed illumination.
EPISCOPALIANS, in the modern ac- ceptation of the term, belong more espe- cially to members of the Church of Eng- land, and derive this title from episcopus, the Latin word for bishop ; or, if it be re- ferred to its Greek origin, implying the care and diligence with which bishops are expected to preside over those com- mitted to their guidance and direction. They insist on the divine origin of their bishops, and other church officers, and on the alliance between church and state. Respecting these subjects, how- ever, Warburton and Hoadley, together with others of the learned amongst them, have different opinions, as they have also on the thirty-nine articles, which were established in the reign of Queen Eliza- beth. These are to be found in most Common Prayer-Books ; and the Episco- pal Church in America has reduced their number to twenty. By some the articles are made to speak the language of Calvi- nism, and by others they have been in- terpreted in favour of Arminianism.
The Church of England is governed by the King, who is the supreme head : by two archbishops, and twenty -four bishops. The benefices of the bishops were con- verted by William the Conqueror into temporal baronies ; so that every prelate has a seat and vote in the House of Peers. Dr. Benjamin Hoadley, however, in a ser- mon preached from this text, " My king- dom is not of this world," insisted that the clergy had no pretensions to tempo- ral jurisdiction, which gave rise to vari- ous publications, termed, by way of emi- nence, the Bangorian Controversy, Hoad- ley being then bishop of Bangor. There is a bishop of Sodor and Man, who has no seat in the House of Peers.
EQU
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Since the death of the intolerant Arch- bishop Laud, men of moderate princi- ples have been raised to the see of Canterbury, and this hath tended not a little to the tranquillity of church and state. The established Church of Ire- land is the same as the Church of Eng- land, and is governed by four archbi- shops, and eighteen bishops.
EPISODE, in poetry, a separate inci- dent, story or action, which a poet invents anH connects with his principal action, that his work may abound with a greater diversitv of events ; though, in a more limited sense, all the particular incidents whereof the action or narration is com- po-.mc'ed are called episodes.
EPITAPH, a monumental inscription in honour or memory of a person defunct, or an inscription engraven or cut on a tomb, to mark the time of a person's de- cease, his name, family, and, usually, some eulogium of his virtues, or good qualities.
EPITHALAMIUM, in poetry, a nup- tial song, or composition, in praise of the bride and bridegroom, praying for their prosperity, for a happy offspring, &c.
EPITHET, in poetry and rhetoric, an adjective expressing some quality of a substantive to which it is joined ; or such an adjective as is annexed to substantives by way of ornament and illustration, not to make up an essential part of the de- scription. "Nothing," says Aristotle, "tires the reader more than too great a redundancy of epithets, or epithets plac- ed improperly ; and yet nothing is so es- sential in poetry as a proper use of them." EPITOME, in literary history, an abridgment or summary of any book, par- ticularly of a history.
EPOC HA, in chronology, a term or fixed point of time, whence the succeed- ing years are numbered or accounted. See CHRONOLOGY.
EPODE, in lyric poetry, the third or last part of the ode, the ancient ode be- ing divided into strophe, antistrophe, and epode.
EPOPOEIA, in poetry, the story, fable, or subject, treated of in an epic poem. The word is commonly used for the epic poem itself. See EPIC.
EPSOM salt, another name for sulphate of magnesia.
EQUABLE, an appellation given to such motions as always continue the same in degree of velocity, without be- ing either accelerated or retarded. When two or more bodies are uniformly acce- lerated or retarded, with the same in-
crease or diminution of velocity in each, they are said to be equally accelerated, or retarded.
EQUAL, a term of relation between two or more things of the same magni- tude, quantity, or quality. Mathemati- cians speak of equal lines, angles, figures, circles, ratios, solids, &c.
EQUALITY, that agreement between two or more things whereby they are de- nominated equal. The equality of two quantities, in algebra, is denoted by two parallel lines placed between them ; thus, 4+2 = 6, that is, 4 added to 2 is equal to 6.
EQUANIMITY, in ethics, denotes that even and calm frame of mind and tem- per, under good or bad fortune, whereby a man appears to be neither puffed up or overjoyed with prosperity, nor dispi- rited, soured, or rendered uneasy, by ad- versity.
EQUATION, in algebra, the mutual comparing two equal things ,of differ- ent denominations, or the expression denoting this equality ; which is done by setting the one in opposition to the other, with the sign of equality ( = ) between them: thus, 3s. = 36 d. or 3 feet = 1 yard. Hence, if we put a for a foot, and b for a yard, we shall have the equation 3 a = bt in algebraical charac- ters. See ALGEBRA.
EQUATIONS, construction of, in alge- bra, is the finding the roots or unknown quantities of an equation, by geometrical construction of right lines or curves, or the reducing given equations into geo- metrical figures. And this is effected by lines or curves, according to the order or rank of the equation. The roots of any equation may be determined, that is, the equation may be constructed, by the intersections of a straight line with ano- ther line or curve of the same dimensions as the equation to be constructed : for the roots of the equation are the ordinates of the curve at the points of intersection with the right line ; and it is well known that a curve may be cut by a right line in as many points as its dimensions amount to. Thus, then, a simple equation will be constructed by the intersection of one right line with another; a quadratic equation, or an affected equation of the second rank, by the intersections of a right line with a circle, or any of the co- nic sections, which are all lines of the se- cond order? and which may be cut by the right line in two points, thereby giving the two roots of the quadratic equation. A cubic equation may be constructed by
EQUATION.
the intersection of the right line with a line of the third order, and so on. But if, instead of the right line, some other line of a higher order be used, then tbe second line, whose intersections with the former are to determine the roots of the equation, may be taken as many dimen- sions lower as the former is taken high- er. And, in general, an equation of any height will be constructed by the inter- section of two lines, whose dimensions multiplied together produce the dimen- sion of the given equation. Thus, the in- tersections of a circle with the conic sec- tions, or of these with each other, will construct the biquadratic equations, or those of the fourth power, because 2x2 = 4; and the intersections of the circle, or conic sections, with a line of the third order, will construct the equations of the fifth and sixth power, and so on. — For example :
To construct a simple equation. This is done by resolving the given simple equa- tion into a proportion, or finding a third or fourth proportional, &c. Thus, 1. If the equation be a x = b c; then a:b::c:x
= — , the fourth proportional to a,6,c. 2.
If a ar=6; then a:b::b:x = — ' a third
a
proportional to a and b. 3. If a x = b* — c* ; then, since b1 — cj = b -}- c X b — o, it Will be q:6
a fourth^ proportional to a, b-\-c, and b — c. 4. If ax = b* + c1 ; then construct the right-angled triangle ABC (Plate V. Mis- eel. fig. 5.) whose base is b, and perpen- dicular is c, so shall the square of the hy- pothemise be A4+c»,' which call h- ; then
the equation is ax=h*t and = — , a third
a proportional to a and h,
To construct a quadratic equation. l.If it be a simple quadratic, it may be reduced to this form, x1 = a b ; and hence a r x :: x -. b, or x = v/ a b, a mean proportional between a and b. Therefore upon a straight line take A B = a, and B C = b; then upon the diameter A C describe a semicircle, and raise the perpendicular B D to meet it in D ; so shall B D be = x, the mean proportional sought between A B and B C, or between a and b. 2. If the quadratic be affected, let it first be x1 -j- 2 ax = b1 ; then form the right-angled triangle, whose base A B is a, and perpen-