I L 



404 ] 



S I L 



is found in the greatest purity in 

 quartz or rock crystal. 

 SI'LICA. A peroxide of Silicon. One 

 hundred parts of silica contain 

 48-4 of silicium, and 51'6 of oxy- 

 gen. It is white ; specific gravity 

 2-6 ; it is fusible. 



SI'LTCATE. A union of silica with 

 some other substance as a base, 

 and by uniting in a double or treble 

 proportion, becomes a bisilicate or 

 trisilicate. The principal silicates 

 are those of alumina, potash, soda, 

 magnesia and lime. 

 SILICIC A'LCE. The quartz agathe cal- 

 cifere of Haiiy : silex silicicalce of 

 Brongniart. A substance occur- 

 ring in amorphous masses, in thin 

 beds, under strata of compact lime- 

 stone in Provence. It is of a grey 

 or brown colour, sometimes nearly 

 black. It effervesces with nitric 

 acid, and before the blow-pipe 

 fuses into a white scoria. It is a 

 mixture of flint and carbonate of 

 lime. 



SILICIOUS SINTER. The Kiesel-sinter 

 of Werner and Klaproth. Quartz 

 agathe concretionnee thermogene of 

 Haiiy. Quartz hyaline concretionee 

 of jBrongniart. An earthy mineral, 

 arranged by some mineralogists as 

 a subspecies of quartz. Its usual 

 colours are white, greyish-white, 

 reddish- white, yellowish- grey, and 

 yellow. According to the analysis 

 of Klaproth it consists of silica 98, 

 alumina 1'5, iron 0'5. Specific 

 gravity 1 '8 1 . It is infusible before 

 the blow-pipe. It is found in the 

 neighbourhood of thermal springs 

 containing silex in solution, and is 

 deposited from them ; more espe- 

 cially by the hot springs of Iceland. 

 SILIC'IFEROUS. (from z%lex t flint, and 

 fero, to bear, yield, or contain, 

 Lat.) Yielding or containing 

 silex ; as the pink siliciferous oxide 

 of manganese. 

 SILI CIFY. To convert into flint ; to 



petrify. 

 SILICIFI'CATION. Called also petri- 



faction. The conversion of any 

 substance into stone by the infil- 

 tration of silicious matter. 

 SILI'CIUM. | Silicon was discovered by 

 SI'IJCON. j Berzelius in 1824. It 

 is of a dark nut-brown colour, 

 without any metallic lustre ; in- 

 combustible in air or in oxygen 

 gas ; but oxidizable by certain 

 methods, by which it is converted 

 into silica or silicic acid. Its 

 equivalent is 7*5 ; its symbol Si. 



" Silicon is now shown not to 

 be a metal, but to be nearly allied 

 to carbon in some of its properties. 

 It will combine with the metals 

 like carbon, especially with alumi- 

 num, forming cast aluminum, as 

 carbon and iron form cast iron." 

 Jukes. The hitherto undecomposed 

 base of silica or silex. Of the 

 metallic bases of the alkalies and 

 earths, silicium is the most abun- 

 dant on the surface of our planet, 

 silica entering so largely into the 

 composition of both chemical and 

 mechanical rocks. 



SILI'CTJLOTJS. Having small pods or 

 husks. 



SI'LIQUA. (Lat.) A pod ; a long 

 seed vessel of two valves, separated 

 by a linear receptacle, on whose 

 edges the seeds are ranged alter- 

 nately. 



SILIQUA'RIA. A genus of marine uni- 

 valves, found both fossil and recent. 

 It is a tubular shell, spiral at its 

 beginning, continued in an irregular 

 form ; divided laterally, through 

 its whole length, by a narrow slit, 

 and formed into chambers by entire 

 septa. Recent siliquariaB have been 

 found in sponges ; they may be 

 distinguished from serpula3 by the 

 longitudinal slit. Cuvier places 

 the genus in the order Tubulibran- 

 chiata. 



SI'LIQTJOSE. } Bearing pods. A term 



SI'LIQUOUS. j applied to plants hav- 

 ing that sort of pericarp denomi- 

 nated a pod or legume. 



SILL. A provincial term signifying 



