REVIEW OF THE BOOK 298 



12. Explain the three great subjects with which agriculture 

 deals. 



13. Is agriculture a science or an art? 



It will be noticed that the body of the book 

 is divided into three co-ordinate parts: the soil, 

 the plant, the animal. These represent the three 

 great fundamentals on which the successful prac- 

 tice of agriculture depends. A complete treatise 

 on agriculture would include a division that 

 would have to do with the general economic 

 principles that underlie the business, and another 

 on the social relations; but the insertion of this 

 discussion would carry the present volume quite 

 beyond its limits of usefulness as an elementary 

 text -book. 



PART I. THE SOIL 



The soil is considered in several aspects. It 

 is important to state at the outset that the pri- 

 mary consideration is not the plant- food alone 

 in the soil, but the physical characteristics as 

 well. In the older books it was customary to 

 place most of the stress on the chemical con- 

 tent of the soil. This was because agricultural 

 chemistry was the first of the natural sciences 

 to make great contributions to the advancement 

 of agricultural knowledge. It is now under- 

 stood that the physical constitution of the soil 

 is as important as its chemical constitution; it 



