JAT 



ICE 



striped and flamed delineations. It occurs 

 in large beds in Saxony, and also in Si- 

 beria, where it is of a very beautiful kind. 

 It admits of a high polish, and is used for 

 purposes of ornament chiefly. It derives 

 its name from the striped colour delinea- 

 tions with which it is marked. The por- 

 celain jasper generally exhibits but a sin- 

 gle colour, and is sometimes marked with 

 cloudy delineations. It melts before the 

 blow-pipe, and is found to consist of 



Silica 60.75 



Alumina 27.25 



Magnesia 3.00 



Oxide of Iron - - - 2.50 



Potash - 3.66 



Loss 



97.16 

 2.84 



100. 



It occurs in beds in pseudo-volcanic 

 hills, and it is supposed that it is slaty clay, 

 converted into a kind of porcelain by the 

 action of fire. It is found in great plenty 

 in Bohemia. 



The common jasper is found generally 

 in veins that occur in primitive rocks in 

 many parts of Europe. It is susceptible 

 of a high polish, and is in considerable re- 

 quest for ornamental purposes. Opal jas- 

 per is found in nests, in porphyry, near 

 Tokay, in Hungary, in the neighbourhood 

 of Constantinople, and in some Siberian 

 mountains. It is supposed to be'the con- 

 necting link between jasper and opal, and 

 is distinguishable by the liveliness of its 

 colours, its superior lustre, and constant 

 conchoidal fracture. 



JATROPHA, in botany, a genus of the 

 Monoecia Monadelphia class and order. 

 Natural order of Tricoccae. Euphorbiae, 

 Jussieu. Essential character : male, ca- 

 lyx none ; corolla one-petalled, funnel- 

 form ; stamina ten, alternately longer and 

 shorter : female, calyx none, corolla five- 

 petalled, spreading ; styles three, bifid ; 

 capsule three-celled ; seed one. There 

 are fourteen species, of which we shall 

 give a short account of the J. elastica, 

 elastic gum-tree ; it is a native of Guiana, 

 of Quito, and Brazil, particularly in Para, 

 where it is called masaradub. The In- 

 dians, by an incision in the bark, extract 

 a viscid white substance, like that which 

 issues from the fig-tree ; they receive it 

 into earthen moulds, to m,ake rings, brace- 

 lets, girdles, syringes, hats, boots, flam- 

 beaux, figures of animals, &c. The abbe 



Rouchon says that the inhabitants of Ma- 

 dagascar also made flambeaux of it, which 

 burn without wicks, and afford them a 

 very good light when t!>ey go out to fish 

 in the night time ; that surgery has de- 

 rived some benefit from it. as it serves to 

 make excellent bandages -, and that in a 

 state of solution it is very pi-oper for coat- 

 ing over silk, to render it impervious to 

 air or water. It has the extensibility of 

 leather, with a very considerable elastici- 

 ty. Spirit of wine makes no impression 

 on this substance, but it dissolves in ether 

 and linseed oil, or in nut oil digested gen- 

 tly in a sand bath : there are also other 

 fat and oily substances which affect it 

 very sensibly. The Chinese have been 

 long acquainted with the art of dissolving 

 it, and of giving it various colours. 



JAUNDICE. See MEDICINE. 



JAY, in ornithology, the variegated 

 corvus, with the covering feathers of the 

 wings blue, variegated with black and 

 white. See CORYUS. 



IBERIS, in botany, candy ~tvft t a ge- 

 nus of the Tetradynamia Siliculosa class 

 and order. Natural order of Siliquosae, 

 or Cruciformes. Cruciferae, Jussieu. Es- 

 sential character : corolla irregular, with 

 the outer petals larger : silicic ernargi- 

 nate, many-seeded. There are fourteen 

 species. 



IBEX, in zoology, an animal of the 

 goat kind, with extremely long nodose 

 horns, which bend backwards, and are 

 of a blackish colour, and annulated on the 

 surface. The body is of a dark dusky 

 colour, and is less in proportion to the 

 height than that of the common goat : it 

 has a great resemblance to the deer 

 kind; the legs are also perfectly like 

 those of the deer, straight, elegant, and 

 slender. It is frequent in many parts of 

 Europe, and, notwithstanding its vast 

 horns, runs and leaps with surprising 

 force and agility. See CAPHA. 



ICE, water in the solid state. When 

 water is exposed to a diminished tempe- 

 rature, itassurhesthe solid state, by shoot- 

 ing into crystals, which cross each other 

 in angles of 60 degrees. During this pro- 

 cess of solidification, the temperature re- 

 mains constant, being 32 degrees of the 

 scale of Fahrenheit. See CALORIC ; also 

 FREEZING. 



During congelation most of the gasi- 

 form fluids, which may have been con- 

 tained in the water, are separated in the 

 elastic form, and exhibit bubbles in the 

 ice, unless the congelation may have been 

 gradually effected from the bottom, or 

 one of the sides; in which case the bub- 



