now CROrS FEED, 



Rocks, conversion into soils 122 



Roots, direct action on soil 320 



Saline incrustations 179 



Saltpeter 252 



Salts decomposed or alisorbod by 



the soil 330 



Sand 153, 102 



Sand filter 172 



Sandstone 121 



Serpentine 114, 121 



Schist, micnceou? 110 



" talcose 121 



chlorite 121 



Shales 122 



Sherry wine re2;i()n 192 



Shrinking of soils laS 



Silica 108 



" function in the soil 353 



" of soil, liberated by strong 



acids 330 



Silicates 109 



" zeolitic, presence in soils.. 349 



Silicic acid, fixed in the soil 358 



Silk, hygroscopic 165 



Soapstone 121 



Sod, temperature of 109 



Soil 104 



" absorptive power of 333 



" aid to oxidation 170 



" aqueous solution of 309, 323, 328 



" condenses gases 105, 166 



" capacity for heat 194 



" chemical action in 331 



" composition of. 302, 369 



" exhaustion of. .373 



" inert basis 305 



" natural strength of. . ., 373 



" origin and formation.. 100, 122, 135 



" physical characters 157 



" porosity of. 170 



" portion insoluble in acids 330 



" relative value of ingredients... .367 



" reversion to rock 332 



" solubility in acids 329 



" " water 309 



" source of food to crops 305 



" state of division 159 



Soils, sedentary 143 



" transported 143 



" weight of 158 



Solubility, standards of 308 



Solution of soil in acids .,370 



" " " water 310 



Steatite 121 



Swamp muck 155 



Suli>hatcs, agents of oxidation 258 



Sulphate of lime 115 



Sulphin-, in decay ..293 



Sulphurous acid 94 



Sulphydric acid 94 



Syenite 120 



Talc lis 



Temperature of soil 1S6, 187, 194 



Transpiration 202, 208 



Trap rock 120 



Ulmates 230 



Ulmic acid 224, 226, 229 



Ulmin 224,226, 229 



Urea 294, 277 



Uric acid 295, 277 



Urine 293 



" preserved fresh by clay 293 



" its nitrogenous principles as- 

 similated by plants 296 



Vegetation, antiquity of 1.38 



" decay of. 137 



" action on soil 140 



Volcanic rocks, conversion to soil.. 135 



Wall fruits 199 



Water absorbed by roots 202, 210 



" functions of, in nutrition of 



plant 216 



" imbibed by soil 180 



" movements in soil 177 



" proportion of in plant, influ- 

 enced by soil 213 



" of soil 315, 317 



" " bottom water 200 



" capillary 200 



" hydrostatic 199 



" hygroscopic 201 



" quantity favorable to crops. .214 



Water-currents 124 



Water-vapor, absorbed by soil. 101, 164 

 " exhaled by plants.... 99 



" not absorbed by 



plants 35, 99 



" of the atmosphere 34 



Weathering 131-134 



Wilting 203 



Wool, hygroscopic 164 



Zeolites 114,349 



