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ICE 



itself sink. It does the same when 

 in danger from any enemy, and 

 like the cuttle-fish, has the power 

 of emitting a coloured fluid, which, 

 by darkening the surrounding 

 water, serves to conceal it from 

 view. If the floating apparatus 

 be injured or destroyed, there exists 

 a reproductive power in the foot, 

 by which it can be restored. 



JA'KGON. (jargon, Fr.) The zircon 

 jargon of Brongniart. A mineral, a 

 variety of zircon: This variety or 

 sub-species of zircon is of a grey, 

 brown, or yellow colour, and is 

 met with in small transparent or 

 translucent prismatic crystals. It 

 is obtained principally from Ceylon: 

 according to the analysis of Vau- 

 quelin, it consists of zirconia 66 '0, 

 silica 31'0, oxide of iron 2'0. 



JA'SPEE. (jaspe, Fr. pierre dure et 

 opaque, de la nature de V agate; 

 jaspide, It.) "Mineralogists have 

 not been able," says Prof. Jameson, 

 " to ascertain the origin of the word 

 Jasper. We only know that it is 

 of high authority, because it occurs 

 in the Hebrew and Greek langu- 

 ages. We are also ignorant of the 

 particular stone denominated Jasper 

 by the ancients." A species or 

 variety of rhombohedral quartz. 

 It is an ingredient in the compo- 

 sition of many mountains. It 

 occurs usually in large amorphous 

 masses, and sometimes also crystal- 

 lized in six-sided prisms. Fracture 

 conchoidal. It is said to compose 

 the substance of entire ranges of 

 the Asiatic mountains. When 

 quartz is combined with a consid- 

 erable proportion of iron and alum- 

 ine, it loses its translucency and 

 becomes jasper. There are many 

 varieties of jasper, distinguished 

 principally by their different col- 

 ours, and the arrangement of those 

 colours. 



Chemically, jasper differs from 

 agate solely in containing a larger 

 portion of iron ; mineralogically, it 



may be distinguished by its opaci- 

 ty. Some mineralogists divide jas- 

 per into five sub-species, namely, 

 Egyptian jasper, striped jasper, 

 porcelain jasper, common jasper, 

 and agate jasper. Jasper is com- 

 monly somewhat less hard than 

 flint, or even common quartz, it 

 will, however, give fire with steel. 

 It is entirely opaque, or, some- 

 times, feebly translucent at the 

 edges ; it presents almost every 

 variety of colour. Specific gravity 

 from 2-30 to 2- 70. It is infusible 

 before the blow-pipe, but loses its 

 colours. With the compound blow- 

 pipe, Professor Silliman says, it 

 fuses into a greyish-black slag with 

 white spots. Jasper is often tra- 

 versed by metallic veins, or by 

 veins of quartz. It sometimes 

 contains fossil shells and marine 

 plants. It is never, says Professor 

 Cleaveland, porphyritic: the base 

 of that, which has been called jas- 

 per porphyry, is fusible, and is 

 either petrosilex or compact felspar. 

 By some it has been supposed that 

 jasper has been formed by the fil- 

 tration of silex into beds of ferru- 

 ginous clay. 



JA'SPER OPAL. The Opal Jaspis of 

 Werner. A sub-species of opal of 

 different shades of red, brown, and 

 yellow, the colour being often dis- 

 tributed in spotted, veined, or 

 clouded delineations. It occurs 

 massive only, and is found in Sax- 

 ony, Hungary, Turkey, and Siberia. 

 Before the blow-pipe it is infusible. 

 Lustre shining, between vitreous 

 and resinous. Fracture conchoidal. 

 Specific gravity from 1-89 to 2'08. 

 According to Klaproth it consists 

 of silica 43-5, oxide of iron 47*0, 

 water 7 '5. 



ICE'BEKG. (from ice and lerg, Germ.) 

 A large mass of ice, met with in 

 cold regions, floating upon the sea, 

 sometimes of an enormous magni- 

 tude and great height. Icebergs 

 have been seen of the great height 



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