E P I
E R I
fubftances feem to confift of a certain combination of the ful- phureous with the iahne principle, which united, not only become the moll irritating ftimuli to the nerves, but act up- on the humours as a putrid ferment in promoting their cor- ruption. Id. ibid. p. 385. See the article Malignant, Append,
EGG (Suppl.) — Sea~EGG, the Englifh name of a fpecies of centronia. See the article Centronia, Suppl.
EGLANTINE, in botany, a name given to the fweet-briar, a fpecies of rofe. See the article Rose, Suppl.
EGLECOPALA, a name fometimes ufed for the ftony, blueifh marie. See the article Marle, Suppl.
ELAEAGNON, or Elaeagnon Tlicophrajli, in botany. See the article Agnus cajlus.
ELATER, the name of a genus of four-winged flies with fe- taceeus antennae; which, when laid on their backs, have a power of leaping with great force and agility.
ELATERIUM, in botany, a name ufed by fome for the mo- mordica of others. See the article Momordica, Suppl.
ELDEN, a word ufed in fome parts of the kingdom for fuel. Diet. Ruff.
ELDER-Zty*, alnus, in botany, the Englifh name of a genus of plants. See the article Alnus, Suppl.
Dwarf-EtDE'Ry in botany, a name given fometimes to the [am- bums of authors. See the article Sambucus, Suppl.
MarJh-'ELDER, or /%rfcr-Ei.DER, the name by which fome writers call the Opulus. See the article Opulus, Suppl.
SpaniJlj-ELDZR, the Englifh name of a genus of plants called by authors Saururus. See the article Saururus, Suppl.
ELEPHAS, the elephant, in zoology. See the article Ele- phant, Suppl.
ELICHRYSUM, in botany, the name of a genus of plants, called in Englifh goldy-lock. See the article Elychrysum, Suppl.
Elichrysum, in botany, is alfo a name given by Tournefort to the gnaphalium, or cut-weed, of Linnaeus. See, the article Gnaphalium, Suppl.
EMPHEREPYRA, in natural hiftory, a genus of ftderochita, compofed of various crufts, or coats, furrounding a nucleus of the fame matter and ftructure with themlelves. Sec the article Siderochita, Append.
Of this genus we have the following fpecies : 1. The very hard fmooth e?npberepyra, with brown, yellow, and red crufts. 2. The hard, glittering, rough empberepyra, with brown, purple, and deepyellow crufts. 3. The foft brownifh-ycllow em~ ■pherepyra. 4. The foft empberepyra, with fhining brown and dufky green crufts. 5. The foft empberepyra, with lucid , whitifh, yellowifh, and red crufts. Hill, Hift. FofT. p. 532,^.
EMPRIMED, among fportfmen, a term applied to a hart when he forfakes the herd. Diet. Ruft. in voc.
ENCAMPMENT. See the article Camp, Append.
ENCEPHALOS, sht<px,Ko<;, in phyfiology, is ufed for. the brain. Cajlel. Lexic. Medic. See the article Brain, CycL
ENCHANTER'S nigbt/bade, a name fometimes given to a ge- nus of plants, called by authors circaa. See the article Cir- cle a, Suppl.
ENCHELIDES, in zoology, the name of a genus of animal- cules, containing the capillary eels, whether of pepper-water, vinegar, &c. See the articles Animalcule, Append, and Pepper, Vinegar, and Eel, Suppl.
ENDEW, in falconry, is faid of a hawk that digefts her meat fo well, that fhe not only difcharges her gorge of it, but even cleanfes her pannel. Diet. Ruft.
ENDIVE, endivia, in botany, a name given to feveral fpecies of cichorlzmu See the article Cichorium, Suppl.
ENGOUTED, in falconry, is faid of a hawk's feathers when they have black fpots in them. Diet. Ruft.
ENHYDRIS, in zoology, a name given by the antient Greeks to the otter, from its living in the water. See the article Lutra, Suppl.
ENHYDRI, in natural hiftory, a genus of cruftated ferrugine- ous bodies, formed into large, and in great part, empty cafes, enclofing a fmall quantity of an aqueous fluid. Of this genus we have only two fpecies : 1. The thick fhell- ed enhydrus, with black, reddifh, brown, and yellow crufts. 2. The thinner fhelled enbydrus, with yellowifh, brown, and purplifh crufts. Hill, Hift. Foft". p. 544.
ENSEELrTJ, in falconry, a term ufed for a hawk which has a thread drawn through her upper eye-lid, and made faft under her beak, to take away the fight. Diet. Ruft.
ENTERING of a bmvk, among falconers, denotes her being
allowed to kill for the firft time. Diet. Ruft. Entering of bounds, istheinftructing them how to hunt. Diet.
Ruft. See the article Entrance, Suppl. ENTERMEW, in falconry. See the article Falcon. ENTERMEWER, among falconers, a hawk which changes
the colours of her wings by degrees. Diet. Ruft. ENTERSELE, in architecture, a kind of fmall ftory, fome- times called a meazanine. Seethe article Mezanine, Cycl. ENTRY, among fportfmen, a term by which fome call thofe places or thickets, through which deer are found lately to have paiTed. Diet. Ruft. EfTLOBIUM, in the Linnaean fyfem of botany, the name of a diftinct genus of plants, called by Tournefort chamanerium. See the article Chamanerium, Suppl.
EQUATION (Suppl.) — Dr. Halley's method for the folutio* of equations is thus :
Let the root z of any equation be taken equal to a ± e ; where a is fuppofed to be taken near to the true value. Then from the quantity a ± e let all the powers of 2 found in the propofed equation, be formed ; and to thefe let their refpective coefficients be prefixed. Let the power to be refolved be fub- du&cd from the fum of the parts of the firft column where e is not found ; and let the difference be ± b. Then take the fum of all the coefficients of e in the fecond column, which call s : and having added all the coefficients of ee, the fum " of which is called r ; the root fought 2, will, in a rational
Form,=tf-|- " and, in an irrational form, — a
— ss±tb y
+ 7' + *^" + *'
t For inftance, let it be propofed to find a root of the equation is 4 -— 322 + 752=10000, where 10000 is the refolvcnd.
d C
For a firft fuppofition let a — 1 ; we fhall therefore have the equation
z A - = a*±4.a' 1 e-]-6a*ee±4.ae :i -\-e* — dzz=. — da^-±.dae — dee + c z =-\~ca±ce
= 10000 ± 40005 4- 6oo? dr 40 e 3 -f- e + ■ — 300 + 600* — 3* + 7501b* 75*
— IOOCO
-f 450 if 40 15* + 597** + 40^ + * + — o
s t u
The figns -f and — with refpect to e and e 3 are left doubt- ful, till it be known whether e be affirmative or negative ; in which there is fome difficulty, as in equations having feveral roots, the bomogenea comparationis, as they are called, are of- ten increafed by diminifhing a, and on the contrary dimim'fh- ed by increafing a. But the fign of e is determined by the fign of the quantity b ; for the refolvcnd being fubtracted from the homogeneum formed from a, the fign of s e, and there- fore of the parts prevailing in its compofition, will always be contrary to the fign of the difference b. Hence it will ap- pear whether e be affirmative or negative, or whether a has been aflumed greater or lefs than the true root. But e is al-
ways eq 1
equal to
ls—\Z*ss—bt
as often as b and / have
t 5
the fame fignj but when, they are connected with different
figns, e becomes =r
%/'rSs + bt — \s
After that e has been
found to be negative, e, e\ e-, &c. rauft be made negative in the affirmative members of the equation ; and affirmative in the negative members, that is, they mult be writ with a contrary fign: but if e be affirmative, then muft: e, e 3 , e 5 , fcfe. be affirmative in the affirmative members, and negative in the negative.
In the propofed example we have 10450 inftead of the refol- vend 10000, or i~ + 4-5° ; from whence it appears that a was taken greater than the true root, and confequently that * is negative. Hence the equation becomes 10450 — 4015* + 597 ee — 4 f 3 +^ 4 = 10000; that is, 450 — 4015* + 597 ^zro. Therefore, 450 = 4015* — 597 e e, or b = st
Is—s/'ss — bt s
■ • - , or — —
/ it
— /** ; the root of which i
7-
— Vthatis,intheprefentcafe,*^ 2QQ7l ~^lZ^il°^ 4'tt / _ _ 597
from whence the approximated root is found to be =r 9.886. Now this root being taken for a fecond fuppolition, and the operation being repeated we fhall have a -f- e — z = 9.8862603936495, which is very exact*, Scarcely exceeding the truth by above 2 the laft figure.
This is fufficient to give a notion of Dr. Halley's method : thofe who defire more examples, and farther inftructions, may confult the Philof. Tranf. N°. 210. or Lowthorp's Abridg. vol. i. p. 85, feq.
Differential ^Equation. See the article Differential, Append.
ERIFFS, a name given to canary birds about two years old. See the article Canary, Suppl.
ERIGERON, in the Linnatan fyftem of botany, the name of a diftinct genus of plants, called by other botanifts conyzoides, conyzella, and [enecionis [pedes j and by us the great fweet flea- bane.
The characters of this genus, accordingto Linnaeus, are thefe: the common cup is oblong, cylindric, imbricated, and befet with fubulated fquama; ; the compofite flower is radiated ; the proper hermaphrodite ones are of an infundibuliform Ihape, the limb being divided into five fegments ; and the proper fe- male ones linear, fubulated, erect, and mod frequently en- tire ; the ftamina of the hermaphrodite flowers are five very fhort capillary filaments, the antherse, cylindraceo-tubulofe ; the germen of the piftil Is extremely fmall ; the ftyle is fill - form j the ftigmata are two, oblong and revokte _; there is
