PREFACE TO THE THIRD EDITION. 



THE rapid exhaustion of the second (1908) edition has given 

 the author an opportunity of fully revising the work and of re- 

 writing certain portions which the advance of knowledge had 

 rendered necessary. 



A few omissions from the former issues have been rectified, 

 andmuch new matter has been added. The book has, in con- 

 sequence, grown considerably in length, but, by an alteration 

 in the type-setting, it has been possible to avoid an increase in 

 the number of its pages. 



Originally, the work dealt with the chemistry and physics 

 of subjects relating, exclusively, to English agriculture, but, 

 in the present edition, some reference has been made to the 

 chemistry of crops of tropical and subtropical countries as well 

 as to questions of stock-feeding in other lands. 



Such inclusions, it is hoped, will not render the book less 

 interesting to the English reader, and may be of service to the 

 actual or intending colonist. 



The arrangement of subjects adopted in the first edition 

 has, with very little change, been followed in the present issue, 

 and the author trusts that the favourable reception accorded to 

 the earlier issues may be extended to this third edition, and 

 that the book may deserve and retain its position as a text- 

 book for those students of agriculture who already possess a 

 fair knowledge of general chemistry. 



The author gratefully acknowledges the valuable help he 

 has received, in the preparation of this edition, from his assist- 

 ant, Mr. James Hill, M.Sc., who has contributed the drawings 

 for several of the illustrations, has greatly helped in the 

 correction of the proof-sheets, and is responsible for the index 

 to this new edition. 



SCARBOROUGH, January , 1913. 



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