CONTENTS 



CHAPTER I. SOIL BUILDERS 



PAGE 



The weathering of rocks ....... 3 



Mountains and stones becoming smaller ... 3 

 Soils being changed into rock . .... 5 



Changes in temperature crack rocks .... 5 



Plants as soil builders 7 



The work of lichens and mosses . . . . ' 7 



Soils built mostly by plants ..... 8 



Stems and roots split rocks ..... 9 



Plants as soil binders ...... 10 



How ice has made soil . . . . . . .11 



Animals as soil builders . . . . . . 12 



The remains of all animals are returned to the soil . 12 



The service of ants, moles, gophers, beavers, etc. . . 13 

 How angleworms improve soil . . . . .14 



The action of moving water ...... 15 



In wearing away a soil and carrying it elsewhere . 16 



The origin of alluvial soils . . . . .17 



In dissolving rocks . . . . . 17 



Soils built wholly or partly by the wind . . . .18 



The soil teems with life 20 



CHAPTER II. THE NATURE OF SOILS 



The fineness of the soil 23 



All soils are becoming finer ..... 23 



The number of particles in different soils ... 23 

 Fineness is richness ...... 25 



The weight of soils ........ 26 



The mineral contents of the soil ..... 26 



The rocks from which soil is made .... 27 

 Elements, compounds and plant food .... 28 



The water in the soil . . v . . . .29 



Free or ground water ...... 29 



Film water 30 



Water absorbed from the air . . . . .31 



