574 INDEX. 



FAGB 



Humus, amount in soils 133 



ash of, from Minnesota soils, analysis 134 



decrease of nitrogen-content with depth , 135 



determination in soils 132 



distribution in the surface soil 157 



functions in soils . , 21 



in arid and humid regions 138 



in black ea^th of Russia 130 



in Minnesota soils 131 



in North Dakota soils 133 



in the surface soil 120 



losses from cultivation and fallow 131 



nitrogen of 124, 135 



percentage in soils, and nitrogen-content of, tables. . .135, 136, 137 



porosity of 1 24 



progressive changes in soils 1 26 



relation to bacterial content 144 



scanty in arid soils, but rich in nitrogen 397 



substances, physical and chemical nature of 124 



variation of, with original materials 139 



volume weight of, table 125 



versus adipocere 140 



Hydraulic elutriation 90 



Hydro-mica 35 



Hydrous silicates in soils of arid region 388 



I. 



Ice-flowers on soils 119 



Immediate plant-food requirements, ascertainment of 333 



productiveness, chemical tests of 337 



productiveness vs. permanent value of soils .318, 327 



India, climatic contrasts 401 



Indian soils, table of analyses 410, 412 



types of soils 411 



Indo-Gangetic plain ; calcareous hardpan, kankar 411 



Injury from excessive runoff, prevention of 220 



to plants from the various salts 531 



to soils and plants from carbonate of soda 78 



Insects, work in soil-formation .... 160 



Insoluble residue of soils ; less in arid than humid 384 



Insufficient rainfall, leaves sea salts in soils 28 



Insular climate, of Britain, western Europe 298 



Introduction xxix 



Injury from swamping, permanent 232 



Iron carbonate solution, how formed 44 



coloring clays 58 



minerals 44 



pyrites, how recognized 75 



