20 THE PRINCIPLES OF 



an idea may appear, it is absolutely and literally true that all 

 animated nature, all animal and vegetable life, has sprung 

 from the soil. The nature of the soil is therefore a subject 

 well worthy of the pen of my illustrious colleague, Professor 

 Huxley, the author of Lay Sermons, and especially of one 

 upon a " lump of chalk," and of another upon " mud." An 

 equally effective lay sermon could be written upon " soil." 



Now, the nature and the origin of the soil are subjects of 

 very deep interest. One point I would at the outset lay 

 stress upon, namely, that the soil, as a substance capable of 

 nourishing and supporting vegetation, must have been pre- 

 paring for thousands, if not millions of years before vegetation 

 was planted upon it. Preparations evidently must have been 

 proceeding for long ages before soils such as we at present 

 see around us could have been produced. The origin of 

 soils is a geological question, but if we ransack works upon 

 geology we shall find but scant attention given to the subject. 

 It is usually dismissed in a paragraph. And, even in books 

 upon agricultural chemistry, the subject is generally all too 

 briefly noticed. We may take it, therefore, that it is left to 

 the agriculturist to study the origin of the soil he tills. I 

 therefore shall discuss at some length the subject of the 

 origin of soil. 



The ordinary explanation given as to the origin of soils is the 

 gradual crumbling down and disintegration of compact rocks, 

 under the operation of various existing natural forces, carried 

 on over an incalculable period of time. These forces are, in 

 a large degree, atmospheric, using the expression in a fairly 

 wide sense. Changes of temperature, for instance, which 

 are perpetually taking place between night and day, as well 

 as between summer and winter, produce alternate contraction 

 and expansion, and substances whicK are exposed to alternate 

 contraction and expansion are apt to break or disintegrate. 

 They are apt to crack up, especially when pressure is brought 



