vi PREFACE 



connecting links. The statistics of imports and production 

 quoted from the official reports of the Board of Agriculture 

 and trade journals, and also accounts of various substances 

 e.g., raw phosphates, ground leather, which the ordinary 

 farmer rarely meets with in that form are perhaps of 

 greater interest from a commercial than a strictly agricul- 

 tural standpoint. They have, however, a certain import- 

 ance and may be considered necessary for completeness in 

 a work of this character. The descriptions of technical 

 processes by which basic slag and some other substances 

 are obtained are intended merely to illustrate the nature of 

 the products and are necessarily much condensed. The 

 prices mentioned in discussing the relative pecuniary value 

 of certain kinds of manure are those prevailing at the time 

 of writing but are not of permanent interest. Instructions 

 for valuing manures issued by the Highland and Agricul- 

 tural Society of Scotland and the estimated manurial value 

 of the commoner kinds of feeding stuffs are given in 

 appendices. The latter is from a recent paper by Dr. 

 Charles Crowther. 



In a few instances analytical methods have been brietly 

 outlined as a convenient plan of developing certain ideas, 

 but details have been avoided. Many of the figures relating 

 to the composition of manures are taken from published 

 reports by Dr. Voelcker and others, but some of them are 

 average results of numerous analyses made by the author. 



The facts and figures selected to illustrate established 

 principles have been chosen, as far as possible, from the 

 Bothamsted records, partly on account of their recognised 

 reliability and partly, also, because these classic researches 

 are likely to prove of greater interest to English students 



