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SCO 



are almost always longitudinally 

 striated. These prisms usually 

 present six, nine, or twelve sides, 

 and are terminated at both ex- 

 tremities by three principal faces. 

 The principal form, not easily 

 obtained by mechanical division, 

 is an obtuse rhomb of which the 

 plane angle at the summit is 

 115 34', or according to some an 

 obtuse rhomboid of 133 Q 50' and 

 46 10'. Phillips terms it a com- 

 bination of silica, alumina, oxide 

 of iron, and lime, with small pro- 

 portions of magnesia, potash, soda, 

 and boracic acid, and the analysis 

 of Gmelin give all these constitu- 

 ents. An attention to its electric 

 powers, its vitreous, conchoid al 

 fracture, and fusibility into an 

 enamel, will generally prevent it 

 from being confounded with other 

 minerals, more particularly from 

 hornblende, which it most resem- 

 bles. 



SCHOBLA'CEOTJS. Eesembling schorl ; 

 containing schorl. The granite of 

 Dartmoor is very frequently por- 

 phyritic from the presence of large 

 crystals of felspar, and here and 

 there shorlaceous. The schorl not 

 unfrequently occurs in radiating 

 nests of variable size and abundance. 



SCHOEL EOCK. A binary compound 

 of schorl and quartz, in which the 

 first considerably predominates. 

 The schorl rock of Cornwall, says 

 Jameson, is probably very inti- 

 mately connected with topaz rock ; 

 its geognostic relations and char- 

 acters are not well ascertained. 



SCHO'ELITE. The Pycnite of Haiiy 

 and Brongniart; the Schorlous 

 beryll of Jameson. A mineral of 

 a straw colour, occurring at Alten- 

 burg, in Saxony, in a rock of 

 quartz and mica. 



SCI'ENCE. (from scientia, knowledge, 

 Lat. science, Fr. sienza, It.) The 

 knowledge of many, orderly and 

 methodically arranged and digested, 

 so as to become attainable by one. 



The knowledge of reasons and 

 conclusions constitutes abstract, 

 that of causes and their effects, 

 and of the laws of nature, natural 

 science. 



SCITAMI'NE.E. One of Linnaeus's 

 natural orders of plants ; they are 

 all natives of warm climates : the 

 ginger, plantain, &e. are examples. 

 Scitamineous plants have been 

 found fossil in the strata of the 

 Isle of Sheppey. 



SCLEE'OBTJS. (from oTcXiy/^os and oov?, 

 Gr. rough-tooth. A genus of fossil 

 fishes, discovered in the upper 

 Ludlow rock, and thus named by 

 M. Agassiz. It may be distin- 

 guished from Psammodus by the 

 raised pustules on the surface of 

 the teeth. 



SCLEEO'TICA. | (from ovcX^os, hard, 



SCLEBO'TIC. ) Gr.) The outermost 

 coat, tunic, or membrane of the 

 eye. It is exceedingly dense and 

 firm, and does not pass over more 

 than about four-fifths of the ball of 

 the eye, its place in front being 

 supplied by a transparent mem- 

 brane, the cornea, to permit the 

 passage of light. 



SCO'LEZITE. A mineral haying one 

 equivalent of hydrated silicate of 

 lime, to one of silicate of alumina, 

 and two of water. 



SCO'PIFOEM. (from scopa, a besom, 

 and forma, form, Lat.) Of the 

 form of a besom or broom. In 

 mineralogy, if a number of minute 

 crystals or fibres be closely aggre- 

 gated into a little bundle, with the 

 appearance of diverging slightly 

 from a common centre, they are 

 said to be scopiform. 



ScoEBfcuLATE. In conchology, pit- 

 ted ; having the surface covered 

 with hollows. 



SCO'EIA. (ffKwpt'a, Gr. scoria, Lat.) 

 The dross or scum of metals ; the 

 cinders of volcanic eruptions (then 

 used plurally, scoria) ; the recre- 

 mentitious matter of metals in a 

 state of fusion. 



