CAMPBELL'S SOIL CULTURE MANUAL 17 



deep within him. He must be saturated with the subject. 

 It must become part of his being, and this can only be ac- 

 complished by going over the subject many times and 

 mastering every detail, always guarding against a wrong 

 understanding of a seemingly minor question. 



The professional man prepares himself for his voca- 

 tion by long study of the books in which are laid down the 

 general principles of his profession or science. The law- 

 yer cons the big books which contain nothing but common 

 sense principles. The engineer or architect or draughts- 

 man spends months in special study of very simple prin- 

 ciples. So also in this science or profession. 



The vital point is ability to understand the soil, its 

 relation to air and water and their combined relation 

 to plant life, and the processes of development of soil 

 fertility, so that the farmer may comprehend fully the 

 effect of various conditions, and the further fact that he 

 himself can by cultivation control these elements; just 

 what, when and how certain work should be done, what 

 to guard against and what to encourage, and what 

 results to reasonably expect. 



The Manual must be studied well. It would be impos- 

 sible to put into a whole library detailed instructions 

 as to every phase of soil culture, adapted to every pos- 

 sible condition that might be encountered; but herein is 

 laid down general principles from which the intelligent 

 farmer can gain an understanding of what should be done. 

 The Manual should be studied every month in the year, 

 and while crops are growing it will pay to consult it every 

 day. 



To further assist the student in grasping all the many 

 principles and details in scientific soil culture we have 

 prepared a correspondence course of twelve lessons through 



