QUESTIONS TO BE CONSIDERED. 189 



investigation of all those phenomena which are presented 

 by the practice of farm-yard manuring. We have to con- 

 sider how form-yard manure increases the produce of a 

 field ; on which constituents of the manure its action de- 

 pends ; what quantity of farm-yard manure can be obtained 

 from a field ; and to what condition, after a series of years, 

 a field can be restored by fiirm-yard manuring. 



It will be understood that from this investigation we 

 exclude all those effects of farm-yard manm-e which can- 

 not be determined by measure and number ; such, for 

 instance, as its influence upon the looseness or cohesion of 

 the soil, and its heating action, by means of the warmtli 

 resulting from the decay of its constituents in the ground. 



The facts, to which this investigation extends, are de- 

 rived from practical experience ; and my selection of them 

 has been materially facilitated by the comprehensive 

 series of experiments made in the year 1851, at the in- 

 stance of Dr. Eexnixg, Secretary-General of the Agri- 

 cultural Society in the kingdom of Saxony, by a number 

 of Saxon agriculturists, with a view of ' ascertaining the 

 action of so-called artificial manures under every variety 

 of condition, for the purpose of more generally extending 

 their application.' These experiments were continued to 

 the year 1854, every series embracing a rotation of rye, 

 potatoes, oats, and clover. The farmers were requested 

 to try bone-dust, rape-cake meal, guano, and farm-yard 

 manure, each on a Saxon acre (=1-3G EngUsh acre) of 

 ground, compared with an unmanured plot of the same 

 size, and to detennine tlie respective crops b}' weight. 



Of all experiments of a similar nature which have 

 been made in the course of several centuries, those which 

 are expressly stated to have been undertaken ' without 

 a direct scientific object' are of the higliest scientific im- 

 portance, not only for their very comprehensive character, 



