PKEF A CE. 



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 knowledge of general chemistry. There has always 

 been difficulty in finding a text-book suited to the require- 

 ments 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, when- 

 ever 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, 

 perhaps, in the arrangement and order of the subject 



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