450 



SILESIA 



SILICON 



Silesian Schools of Literature, see GERMANY ( Vol. 

 V. |.. 187), and Omx. 



Bee Griinlugen's tlrtchtehU StUerien* (2 rob. Gothm, 

 1884-80); A<Umy' SeUetien naekttinen iJiiuikalinrhen, 

 tOpaorapkuelten.uiulitalMuehen VerkaltnitKn (6th ed. 

 BresUn, 18*5) ; and Schroller't SeUetien (3 vola. Ulogau, 

 1 ^:, s- 



Silesia. AUSTRIAN, a duchy and crown-land 

 of the Austrian empire, t>ounded cm the NE. by 

 Pin -jan sili-iu, ami on the S. and \V. liv Moravia 

 and Hungary. Area, 1987 sq. in.: pop. (1880) 

 085,475 ; ( 1890) 602,1 17. Subsidiary chains of the 

 Carpathians and Sudetic Mountains diversify the 

 southern and western frontiers ; the duchy is 

 watered by the systems of the Vistula (in the 

 east ) and the Oder ( west ). The climate, though 

 somewhat raw, is healthy, and the soil produces 

 good crops of rye, oat*, barley, potatoes, beet-root, 

 hay, &c. Muting and manufacturing industries 

 both flourish. The mines yield coal, iron, sulphur, 

 and other minerals to the annual value of close 

 upon one million sterling. The principal industries 

 are the smelting of iron, making of machinery, the 

 manufacture of various textiles (worsted, cloth, 

 linen and linen threat!, cottons, &C.), brewing, dis- 

 tilling, and the preparation of chemicals. The 

 principal town is Troppau. This province was 

 created a separate crown-land in 1849. There is 

 a provincial assembly or diet of thirty-one 

 members. 



Silex (Lat., 'flint'), a generic name given by 

 some mineralogists to all those minerals of which 

 silica is the principal ingredient. See SILICON, 

 QUARTZ. 



si MH-I. See SYLHET. 



Silhouette, a profile or shadow-ontline filled in 

 of a dark colour, the shadows and extreme depths 

 being sometimes indicated by the heightening effect 

 of gum or some other shining material. This 

 speciea of design was known among the ancients, 

 and was by them carried to a high degree of per- 

 fection, as the monochromes on Etruscan vases 

 amply testify ; but the name silhouette is quite 

 modern, dating from aliont the middle of the 18th 

 century, though the art itself seems to have been 

 practised in England prior to 1745. It was taken 



from Etienne 

 de Silhouette 

 (1709-67), the 

 French minister 

 of finance for four 

 months in 1759, 

 who, to replenish 

 the treasury, ex- 

 hausted by the 

 costly ware with 

 Britain and Prus- 

 sia, and by ex- 

 cessive prodigal- 

 ities, inaugur- 

 ated numerous 

 reforms and the 

 strictest econ- 

 omy of ex|H*ndi- 

 ture. His earli- 

 est reforms were 

 admirable ; his 

 later ones, how- 

 ever, were so 

 capricious, short- 

 sighted, and un- 

 successful that 



he fell utterly from favour, and his name became 

 a byword for injudicious parsimony ; any mode 

 or fashion that was plain and cheap was stvli-d 

 (i IK Silhouette; and profiles made by tracing 

 the ihadow projected by the light of a candle 



of Robert Hnrnn. 



on a sheet of white paper, the rest of the figure 

 living tilled tip in black, have continued to 

 bear tin- name. Although without merit as a 

 work of art, the silhouette presents a clear and 

 "II marked profile, and the Pantagraph (q.v.) 

 used to be frequently employed to obtain profiles 

 of a reduced size direct from the human features. 

 Profiles cut out of black pnj>er with scissors also 

 receive the name of silhouettes ; and akin to these 

 are the 'silhouette illustrations ' to J-'mi.'.t, A Mnl- 

 summer Night's Dream, &c., by the Prussian Paul 

 Konewka (1840-71), or those to our own article 

 HORSE in Vol. V. p. 794. It should be added 

 that Lit inj derives the use of the word otherwise : 

 quoting from the Journal OfRciel of 1869 a state- 

 ment that one of M. de Silhouette's chief amuse- 

 ments after his fall was making such shadow- 

 portraite, and that his chateau of Bry-sur-Marne 

 had the walls of several of its rooms adorned with 

 pictures of this sort. M. de Silhouette was at an 

 earlier date secretary and chancellor to the Duke 

 of Orleans, and was one of the three commissioners 

 appointed in 1749 to delimit the frontiers of the 

 I'rench and British possessions in Acadin. He 

 wrote a number of works, and published three 

 translations from the English of Boungbroke, Pope, 

 and AVarburton respectively. See a long corre- 

 spondence in Notes and Queries for 1882-83. 



Silica. See SILICON. 



Silicon, or SILICIUM, is one of the non-metallic 

 elements : sym. Si ; at. wt. 28'4 (O = 16) ; sp. gr. 

 of crystalline form, 2'49. It may be obtained 

 in three different forms viz. the amorj>hous, the 

 grrijihitoitl, and the crystalline. It is amorphous 

 silicon which is obtained by the processes in com- 

 mon use, the other forms being obtained from it. 



Amorphous silicon presents the appearance of a 

 dull brown powder, which adheres to the finger, is 

 insoluble in water and in nitric and sulphuric acids, 

 but readily soluble in hydrofluoric acid and in a 

 hot solution of potash. It is a non-conductor of 

 electricity, and when heated in air or oxygen it* 

 external surface burns brilliantly, and is converted 

 into silica, which fuses from the extreme heat, ami 

 forms a coating over the nnhnrned silicon. Grny/A- 

 itoid silicon is obtained by exposing the amorphous 

 variety to an intense heat in a closed platinum 

 crucible. This form of silicon will not take fire 

 when heated in oxygen gas, and resists the solvent 

 action of pure hydrofluoric acid, although it rapidly 

 dissolves in a mixture of nitric and hydrofluoric 

 acids; moreover, it is a conductor of electricity. 

 Deville obtained crystallised silicon in regular 

 double six-sided pyramids of a dark steel-gray 

 colour. 



Silicon, in a state of combination with oxygen, is 

 the most abundant solid constituent of our globe ; 

 in less proportion, is an equally necessary ingre- 

 dient of tne vegetable kingdom ; while in the 

 animal kingdom it occurs in mere traces, except in 

 a few special eases. It is never found in nature 

 except in combination with oxygen ; but, by a 

 somewhat dillicult process, it may be separated as 

 a dark brown powder. It was first isolated by 

 Iter/eliits in 18'2:t. For our knowledge of the 

 other modifications we are indebted to AA tihler and 

 Deville. 



Silicon forms two oxides, one of which is only 

 known in the hydrated state, while the other is 

 the well-known compound silica or silicic arid. 

 Silica or silicic acid is represented by the formula 

 SiO,, and a hydrate, 3HO,2SiO 2 , has been obtained, 

 while other h'ydrates are known to exist. 



Silica exists both in the crystalline and in the 

 amorphous form. The best examples of the crys- 

 talline form are rock-crystal, quartz, chalcedony, 

 flint, sandstone, and quartzose sand. Silica in this 



