XXXli INTRODUCTION 



enable him to live in some epoch of an unequally devel- 

 oped society; and if there are or have been such social 

 epochs, then is society itself directly responsible for the 

 waste of the common heritage. 



On every side, therefore, it is important that we study 

 the soil. Beyond all mere technical agricultural practice, 

 the principles of soil management must be compre- 

 hended and taught. There is no good sociology that does 

 not recognize this fact. 



We tend always to discuss great subjects from one 

 point of view. So has the soil usually been treated from 

 the chemical point of view, from the geological, from the 

 agricultural. In this book, the authors have attempted 

 to discuss the soil in all its relations to plant production, 

 developing the inter-dependence of geological, chemical, 

 bacteriological, physical and industrial relationships in 

 such a way as to give the student a grasp, albeit a brief 

 one, of the entire subject in its many bearings. In its 

 treatment, the book considers, first, the soil as a medium 

 for root development ; second, as a reservoir for water ; 

 third, as a source of nutrients; fourth, as a realm of 

 organisms; fifth, in its relation to air; sixth, its relation 

 to heat; and the relation of man to the soil follows as a 

 consequence and conclusion. 



The past few years constitute a period of great activity 

 in the study of the soil, so much so that many of our most 

 established opinions have been challenged. Perhaps it 



