EXT 



EYE 



equation it appears that a x = c b y, 



and x = 



C ~~ 



and from the second 



M 



equation, that d x = / c y, and x = 



d ' a d 



and c d d b y = a f a e y, whence 

 a e y d b y = fl / c d\ and y = 

 afc d 



a e d b 



To exemplify this theorem, suppose a= 

 5, 6=7, c = 100, d = 3, e 8, ancl/ = 



5 X 

 80. Then y = j-^ 



100 _ 5 



5; and x = -.-5-= 13=-, 



83 

 240 

 19 19' 19~ 19 



If three or four equations are given, in- 

 volving three or four unknown quantities, 

 their values may be found much in the 

 same manner. 



EXTERNAL medicines, the same with 

 local or topical medicines. 



EXTERNAL angles, are the angles on 

 the outside of any right-lined figure, 

 when all the sides are severally produced, 

 and they are all, taken together, equal to 

 four right angles. 



EXTINGUISHMENT, in law, where- 

 ever a right, title, or interest is destroyed, 

 or taken away by the act of God, opera- 

 tion of law, or act of the party, it is called 

 an extinguishment; a creditor's accepting 

 a higher security than he had before is 

 an extinguishment of the first debt. 



EXTORTION, in law, any oppression 

 by colour or pretence of right. 



EXTRA judicial, in law, is when judg- 

 ment is given in a cause or case not de- 

 pending in that court, where such judg- 

 ment is given, or wherein the judge has 

 no jurisdiction. 



EXTRA parochial, out of any parish; 

 privileged or exempted from the duties 

 of a parish. 



EXTRACT, in pharmacy, the soluble 

 parts of vegetable substances, first dis- 

 solved in spirit or water, and then re- 

 duced to the consistence of a thick 

 syrup or paste, by evaporation. See 

 PHARMACY. 



EXTRACTION, in chemistry, is the 

 general operation, by means of which we 

 separate and extract from very com- 

 pounded bodies of the vegetable and 

 animal kingdoms, different matters con- 

 tained in them. For this purpose alco- 

 hol, water, acids, and alkalies, are made 

 use of. Therefore extraction is perform- 

 ed by dissolutions, macerations, infusions, 

 &c. 



EXTRACTION, in surgery, is the draw- 

 ing any foreign matter out of the body 

 by the hand, or by the help of instru- 

 ments. 



EXTRACTION, in genealogy, implies the 

 stock or family from which a person is 

 descended. 



EXTRACTION of roots, in algebra and 

 arithmetic, the method of finding the 

 root of any power or number. See AL- 

 GEBRA. 



EXTRACTOR, in midwifery, an in- 

 strument or forceps, for extracting child- 

 ren by the head. See MIDWIFERY. 



EXTRAVASATION, in contusions, fis- 

 sures, depressions, fractures, and other 

 accidents of' the cranium, is when one or 

 more of the blood-vessels that are distri- 

 buted on the dura mater is broke or di- 

 vided, whereby there is such a discharge 

 of blood as greatly oppresses the brain, 

 and disturbs its offices; frequently bring- 

 ing on violent pains, and other mischiefs; 

 and, at length, death itself, unless the 

 patient is timely relieved. 



EXTREME and mean proportion, in 

 geometry, is when a line is so divided in- 

 to two parts, that the rectangle under the 

 whole line, and the lesser segment, is 

 equal to the square of the greater seg- 

 ment. 



EXUVIAE, among naturalists, denote 

 the cast-off parts or coverings of animals, 

 as the skins of serpents, caterpillars, and 

 other insects. See ENTOMOLOGY. 



M. Reaumur is very particular in de- 

 scribing the manner in which the cater- 

 pillar tribe throw off, or extricate them- 

 selves from their exuviae. See vol. i. of 

 the "History of Insects.'* 



The crab, some spiders and phalangii, 

 as is well known, can even throw oft' 

 their limbs at pleasure, which are again 

 replaced by new ones. See CANCER. 



EXCVIJE is also used for the remains of 

 sea animals, found fossile, and more pro- 

 perly called extraneous, or marine fossils, 



EYE. See ANATOMY and OPTICS. 



EYE, in architecture, is used to signify 

 any round window made in a pediment, 

 an attic, the reins of a vault, or the like. 



EYE of a dome, an aperture at the top 

 of a dome, as that of the Pantheon at 

 Rome, or of St. Paul's at London : it is 

 usually covered with a lantern. 



EYE, in agriculture and gardening, sig- 

 nifies a little bud, or shoot, inserted into a 

 tree, by way of graft. 



EYE of a tree, a small pointed knot to 

 which the leaves stick, and from which 

 the shoots or sprigs proceed. 

 See EUPHBASIA, 



