HYP 



HYR 



HYPEHBOLIC line, is used, by some au- 

 thors, for what we call the hyperbola it- 

 self. In this sense, the plane surface, 

 terminated by the curve line, is called 

 the hyperbola, or hyperbolic space ; and 

 the curve line that terminates it the hy- 

 perbolic line. 



HYPERICUM, in botany, St. John's 

 wort, a genus of the Polydelphia Polyan- 

 dria class and order. Natural order of 

 Rotaceae. Hyperica, Jussieu. Essential 

 character : calyx five-parted ; petals five ; 

 filaments many, connected at the base in 

 five bundles. There are fifty-seven spe- 

 cies. These are principally shrubs or 

 under shrubs, with cylindrical, ancipital, 

 or quadrangular stems; leaves frequent- 

 ly with pellucid dots; flowers, sometimes 

 in cymes, frequently in corymbs, with the 

 peduncles often trichotomous and three 

 flowered, 



HYPHYDRA, in botany, a genus of the 

 Monoecia Gynandria class and order. Es- 

 sential character : male, calyx one-leafed, 

 three parted; corolla none ; stamens six, 

 inserted above the germ; female, calyx 

 and corolla none ; style triangular, with 

 three stigmas; capsule one-celled, three- 

 valved ; seed single. There is but one 

 species, viz. H. fluviatilis, a little plant 

 which grows three or four feet under wa- 

 ter; it is a native of Guiana. 



HYPNUM, in botany, a genus of the 

 Cryptogamia Musci class and order. Na- 

 tural order of Musci or Mosses. Generic 

 character : capsule oblong ; peristoneum 

 double, outer with sixteen broadish teeth, 

 inner membranaceous,equally lanciniated; 

 segments broadish, with capillary ones in- 

 terposed. Males germaceous, on differ- 

 ent plants. Botanists differ greatly as to 

 the number of species; some reckon forty, 

 others fifty, and Dr. Withering enume- 

 rates seventy, and to facilitate the investi- 

 gation of the species, he has thrown them 

 into seven divisions. 



HYPOCHOERIS, in botany, a genus 

 of the Syngenesia Polygamia ^Equalis 

 class and order. Natural order of Com- 

 positae Semiflosculosae. Cichoraceae, Jus- 

 sieu. Essential character : calyx subim- 

 bricate ; down feathered ; receptacle 

 chaffy. There are five species. 



HYPOTHEC ATE, in law, to hypothe- 

 cate a ship, is to pawn the same for ne- 

 cessaries; and a master may hypothecate 

 either ship or goods for relief, when in 

 distress at sea; for he represents the 

 traders as well as owners ; and in whose 

 hands soever a ship or goods hypothe- 

 cated come, they are liable. But it has 

 been recently held in the court of King's 



Bench, that if the master pay for the re- 

 pairs himself, and do not hypothecate the 

 ship, he has no lien upon the ship for his 

 debt. 



HYPOTHENUSE, in geometry, the 

 longest side of a right angled triangle ; or 

 it is that side which subtends the right 

 angle. Euclid, lib. i. proposition 47, de- 

 monstrates, that in every rectilinear right 

 angled triangle, the square of the hypo- 

 thenuse is equal to the squares of both 

 the other sides. This celebrated pro- 

 blem was discovered by Pythagoras, 

 who is said to have sacrificed a heca- 

 tomb to the Muses, in gratitude for the 

 discovery. 



HYPOTHESIS, in general, denotes 

 something supposed to be true, or taken 

 for granted, in order to prove or illus- 

 trate a point in question. An hypothesis 

 is either probable or improbable, ac- 

 cording as it accounts rationally or not 

 for any phenomenon ; of the former kind 

 we may reckon the Copernican system 

 and Huygens's hypothesis concerning 

 the ring of Saturn ; and the Ptolemaic 

 system may be esteemed an instance of 

 the latter. 



HYPOXIS, in botany, a genus of the 

 Hexandria Monogynia class and order. 

 Natural order of Coronariae. Narcissi, 

 Jussieu. Essential character : calyx a 

 two valved glume ; corolla, six-parted, 

 permanent, superior ; capsule narrower 

 at the base. There are fourteen species. 



HYRAX, in natural history, a genus of 

 Mammalia, of the order Glires. Generic 

 character: front teeth in the upper jaw 

 two, broad and somewhat distant ; in the 

 lower jaw four, broad, flat, contiguous, 

 and notched; grinders large, four on i 

 each side in both jaws ; fore-feet four- 

 toed, hind feet three-toed ; no tail ; no 

 clavicles. What distinguishes this genus 

 from the whole class of Glires, besides, is 

 the circumstance of having four teeth in- ' 

 stead of two in the lower jaw, and in- 

 deed the teeth in general are differently 

 formed. There are two species. 



H. capensis, or the Cape hyrax, is 

 about as large as a rabbit, and abounds 

 in the mountainous districts near the 

 Cape of Good Hope, leaping from rock to 

 rock with extreme agility, feeding by day, 

 and retreating at night to the clefts and 

 holes of the mountains. It has no power 

 of burrowing any recess for itself. Its 

 sound is a reiterated squeak. It sub- 

 sists entirely on vegetable food, and 

 prepares a bed for its repose and com- 

 fort in its favourite recess. It may be 

 easily familiarized, and in a state of 



