QUESTIONS TO BE CONSIDERED. 185 



dition, after a series of years, a field can be restored by 

 farm-yard manuring. 



It will be understood that from this investigation 

 we exclude all those effects of farm-yard manure which 

 cannot be determined by measure and number ; such, 

 for instance, as its influence upon the looseness or cohe- 

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

 warmth resulting from the decay of its constituents in 

 the ground. 



The facts, to which this investigation extends, are 

 derived from practical experience ; and my selection of 

 them has been materially facilitated by the comprehen- 

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

 instance of DR. KENNING, Secretary-General of the 

 Agricultural Society in the kingdom of Saxony, by a 

 number of Saxon agriculturists, with a view of ' ascer- 

 taining the action of so-called artificial manures under 

 every variety of condition, for the purpose of more gen- 

 erally extending their application.' These experiments 

 were continued to the year 1854, every series embra- 

 cing 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*36 English acre) of ground compared with 

 an unmanured plot of the same size, and to determine 

 the respective crops by 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 highest 

 scientific importance, not only for their very compre- 

 hensive character, but because they have resulted in 

 fully establishing a number of facts which will for all 

 time to come retain their validity as safe bases for 

 scientific conclusions. Science owes the deepest grati- 

 tude to the excellent propound er of these inquiries, and 

 to the worthy men who so zealously performed their 

 task ; the only thing to be regretted is, that the experi- 

 ments upon unmanured plots were not carried out in 

 all cases. 



