PREFACE TO THE FIRST EDITION. 



THE present volume is based upon lectures delivered annually 

 for several years past, by the author, to classes of. agricultural 

 students, many of whom had already acquired some know- 

 ledge of general chemistry. There has always been difficulty 

 in finding a text-book suited to the requirements of such 

 students. An attempt has therefore been made in this work to 

 present to the reader some, at least, of the many problems of 

 agriculture on which chemistry and physics may throw light. 

 In all cases, the writer has endeavoured to avoid empiric 

 statements, and to give, as far as possible, an explanation of 

 the facts or phenomena described. 



Current literature has been freely consulted, and whenever 

 possible, reference to the source of the information has been 

 given. In some few instances, perhaps, this may not have 

 been done, for in the preparation of lecture notes it often 

 happens that matter is incorporated without a record of its 

 origin being made. In most cases, the original paper is named 

 and, if foreign, the abstract in the Journal of the Chemical 

 Society, or in the Journal of the Society of Chemical Industry 

 has, if possible, also been quoted. 



Much originality is not expected in a manual, except, per- 

 haps, in the arrangement and order of the subject matter ; but 

 the author ventures to hope that not only is the book novel in 

 scope and style, but that certain views therein expressed are 

 original and may prove of service. Thus, in the introductory 

 chapter, the account of the distribution and relative abundance 

 of the elements contains some ideas, not, so far as he is aware, 

 to be found elsewhere. Chapters IV., X., 1 and XIV., 2 too, will 

 be found to contain matter not generally available. 



Osmosis and diffusion appear to be commonly regarded by 

 botanists as synonymous terms, and much confusion seems to 

 exist as to the parts which osmotic pressure and diffusion play 

 in the processes of plant life. 



1 XL in the third edition. 2 XV. in the third edition. 



