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SOD 



described under the article " elementary 

 substances." The mineralogist and the 

 geologist consider those minerals as simple 

 and homogeneous, which present no dif- 

 ference of qualities to our senses through- 

 out the mass, although the chemist may 

 discover that such minerals are composed 

 of two or more elementary substances. 

 The difference between a simple mineral 

 and a simple substance may be illus- 

 trated by the case of calcareous spar, or 

 crystallized carbonate of lime. The ulti- 

 mate elements, calcium, oxygen, and car- 

 bon, are simple substances , the crystal- 

 line compound resulting from the union 

 of these elements, forms a simple mineral, 

 called carbonate of lime. Bakewell. 

 Buckland. 



SINI'STRAL. A term applied to shells, 

 where, in consequence of the heart 

 being placed on the right side, the turns 

 of the spiral are made to the left. 

 These shells are termed sinistral, or re- 

 versed. 



SI'NTER. (sinter, Germ, a mineral sub- 

 stance ; scale which flies from the iron 

 while it is under the hammer.) Cal- 

 careous sinter is a variety of carbonate of 

 lime, and may be either stalactical, tu- 

 berose, reniform, globular, cylindrical, 

 tubular, branched, or in large, undulated, 

 masses. It is composed, whatever may 

 be its form, of a series of successive 

 layers, concentric, plane, or undulated, 

 and nearly or quite parallel. Quartzy 

 sinter, or pearl sinter, is a variety of 

 opal. 



SI'NUATE. > (sinuatus, Lat.) In botany, 



SI'NUATED. $ applied to leaves when the 

 margins are cut into wide rounded open- 

 ings, as in the leaf of the oak. 



SI'NUOUS. (sinuev,x, Fr. sinuoso, It.) 

 Bending in and out ; winding ; crooked ; 

 tortuous. 



SI'NUS. (sinus, Lat. a bag, sinus, Fr.) 

 ] . In anatomy, a cavity or cell ; a narrow 



2. In conchology, a groove or cavity. 



SI'PHON. ) (siphon and siphunculus, 



SI'PHUNCLE. \ Lat. siphon, Fr. sifone, 

 It.) An hydraulic apparatus belonging 

 to chambered, or polythalamous, shells, 

 passing through the several chambers, 

 and terminating in a large sac, which 

 surrounds the heart of the animal. The 

 use of the siphunculus appears to be the 

 enabling the animal to rise to the surface, 

 or descend to the bottom, of the water, by 

 increasing its specific gravity. 



SI'PHUNCLED. Possessing a siphuncle ; 

 formed with a siphuncle. 



SKO'RODITE. (from ffKopodov, gaiiick, Gr.) 

 A mineral of a leek-green or brown co- 

 lour ; an arseniate of iron. Before the 

 blow-pipe it fuses, giving out a smell of 



garlick, from which circumstance it has 

 obtained its name. 



SKO'RZA. The epidote skorza of Brong- 

 niart ; epidote arenace of Hatty. A va- 

 riety of epidote. 

 SLAG, (schlacke, Germ, slagg, Dan.) The 



drop or recrement of metal. 

 SLATE. A kind of clay, of a structure 

 termed schistose, which admits of being 

 split into thin layers of considerable ex- 

 tent. Slate is commonly of a bluish or 

 greenish colour, with a silky lustre. It 

 consists of silex 50'0, alumina 25'0, 

 oxide of iron ITS, manganese 1'6, potash 

 4*8, carbon 0'3, water 75. It is opaque ; 

 may be scratched by the knife ; and fuses 

 into a blackish slag. 



SLA'TY. Resembling slate ; containing 

 slate ; composed of parallel thin plates 

 which admit of being separated by split- 

 ting. 



SLATE SYSTEM. This group is sub-divided 

 into, 1st, the Plynlymmon rocks, con- 

 sisting of grauwacke and grauwacke slate, 

 with beds of conglomerates, the thick- 

 ness of the whole being estimated at 

 several thousand yards. 2nd, The Bala 

 limestone, a dark limestone associated 

 with slate, containing shells and corals. 

 3rd, The Snowdon rocks, consisting of 

 fine-grained slates, of various shades of 

 colour, and of fine and coarse grauwacke 

 and conglomerate. In the strata of the 

 slate system are found the most ancient 

 organic remains. 



SLI'CKENSIDES. A provincial name for a 

 variety of galena, 



SLOTH. The Bradypus of Linnaeus, the 

 only existing genus of Tardigrada. 



SMALT, (smalto, It. schmalte, Germ.) 

 Powder-blue, a vitreous substance ob- 

 tained by melting zaffre, silex, and potash 

 together. 



SMARA'GDITE. The name given by Saus- 

 sure to diallage. 



SMA'RAGD. ) (from oyxapay^oc, Gr. sma- 



SMARA'GDUS. $ ragdus, Lat. smeraldo, 

 It. smaragd, Germ.) The emerald. See 

 Emerald. 



SOA'PSTONE. A name given to steatite, in 

 consequence of its soapy feel. Its de- 

 scription will be found under the word 

 Steatite. 



SO'DA. (soda, sode, soude, Germ.) Mi- 

 neral fixed alkali, found native in some 

 situations, but generally obtained from 

 the combustion of marine plants, more 

 particularly of the salsola soda. Com- 

 mon salt, so universally employed as a 

 condiment and as an article of food, so 

 absolutely necessary to the preservation 

 of health, is a chloride of sodium, con- 

 sisting of 52'26 parts of soda, and 45 - 74 

 parts of hydrochloric acid. Soda, says 

 Mr. De La Beche, is found in schorl, and 



