398 



INDEX 



Seaeoast swamps, reclamation of, 



327 

 Secondary constituents of rocks, 

 10 



rocks defined, 47 

 formation of, 47 

 Sedentary materials, 288 

 Sedimentary deposits, 112 



rocks, classification, 113 

 defined, 49 

 Sedimentation, process of, 48 

 Selenite, 109 

 Septarian nodnle, 33, 106 

 Sericite as a rock constituent, 22 

 Serpentine as a rock constituent, 27 



derived from olivine, 23 

 pyroxene, 107 



origin of, 137 



weathering of, 209 

 Shales, composition and origin, 120 

 Shale, word defined, 120 

 Shell limestone, 125 



weathering of, 219 



marl, 128 

 Sheets, intrusive, 46 

 Silica, 103 



lost during weathering, 220 

 Siliceous sinter, 103 



group of rocks, 123 

 Silicon as a constituent of the 



earth's crust, 5 

 Sills, 46 



Silt from granite, analyses of, 191 

 Singing sands, 125 

 Sinkholes, formation of, 247 

 Slates, 119 



roofing, origin of, 135 

 Slickensides, defined, 49 

 Snow, dust in, 332 

 Soapstone, analyses of, 211, 212 



composition of, 95 



origin of, 95 



weathering of, 211 

 Sodium as a constituent of the 

 earth's crust, 6 



chloride, 111 

 Soil, the, 345 



capacity for water, 368 



chemical nature of, 345 



creep, 274 



definition of, 3 



fertility, cause of, 349 



inorganic nature of, 346 



temperatures at varying depths, 

 162 



water contents of, 267 

 Soils, affected by plants and animals, 

 378 



Soils, alkali of, 359 



action of frost on, 356 



cause of color variation, 374 



classification, 371 



color of, 373 



colloidal matter of, 365 



compared with the mother rock, 



348 

 essential constituents of, 350, 



351 

 fertility dependent on physical 

 conditions, 368 

 due to lime, 355 

 grains in one gram, 367 

 interspaces of, 367 

 leaching of, 356 

 mineral nature of, 362 

 nitrates in, 360, 361 

 nitrogen of, 360 

 of arid regions, 357 



and humid regions com- 

 pared, 356-359 

 of Seychellian island, 362 

 physical condition of, 367 

 regur of India, 372 

 residual, analyses of, 347 

 ruined by erosion, 386 

 soluble matter in, 354, 365, 



366 

 soluble salts in, 357 

 water capacity of, 368, 370 

 weight of, 371 

 wind drifted, 284 

 zeolites in, 363 

 Solution, amount lost in, 245 



of rocks, 168 

 Specific gravity of rocks, 40 

 Spheroidal structure due to weather- 

 ing, 232 

 Sphagnous deposits, thickness of, 306 

 Sphagnum, rate of growth in bogs, 



305 

 Spilite, 85 

 Stalactites, 106 

 Stalagmites, 106 

 Steatite, 108 



Stone Mountain, G-a,, weathering of, 

 231 

 implements, weathering of, 260 

 Stratified, or bedded rocks, 141 

 Structure of rocks, 30 

 Subsoil, defined, 373 

 Sulphur as a constituent of the 



earth's crust, 8 

 Sulphuric acid, corrosive effects of, 



172 

 Surface contours incidental to wea- 

 thering, 246 



