150 LETTER-FILES OF S. W. JOHNSON 



During the years beginning with 1864 and ending 

 with 1870, Professor Johnson wrote three books. 

 "Peat and its Uses as Fertilizer and Fuel" grew out 

 of work begun in the interests of the Connecticut 

 Agricultural Society. Published in 1866, this book 

 was, in 1910, referred to in the columns of a leading 

 agricultural journal as still true and useful, contain- 

 ing all that could today be said on the subject, the 

 writer regretting because of this fact that it is now 

 out of print. 



Professor Johnson had devoted the best powers of 

 his mind to collecting and arranging the conflicting 

 evidence on record in the literature. Therefore he 

 could teach his subject with such certainty as the true 

 state of knowledge permitted. The results of his 

 studies were set forth in the two volumes, ' ' How Crops 

 Grow" and "How Crops Feed." 



"How Crops Grow. A Treatise on the Chemical 

 Composition, Structure and Life of the Plant, for all 

 Students of Agriculture," which was published in 

 1868, has been perhaps more widely read and studied 

 than any other work on agricultural chemistry. It 

 gave a new basis for the teaching of agriculture as 

 well as a broader understanding of the principles and 

 the reasons of farm practice. In his preface the 

 author said: 



Agricultural Chemistry has ceased to be the monopoly of 

 speculative minds and is well based on a foundation of hard 

 work in the study of facts and first principles. Vegetable 

 Physiology has likewise made remarkable advances, has dis- 

 encumbered itself of many useless accumulations and has 

 achieved much that is of direct bearing on the art of 

 cultivation. 



