ON MANURES. 



43 



crops, it has been observed, in the treatise to which we have 

 already alluded, that the statement is only entitled to weight 

 upon the construction either that some of the manure made on 

 the farm tliat was expended under the old system is disposable 

 for some other purpose under the new ; or that some expense 

 in fetching manure from distant places, that had used to be 

 iniiurred, is saved. For, if the assertion 'that his crops have 

 been as good as ev5r they w^ere, and go nearly twice as far,' 

 means only that the dung when now expended is nearly twice 

 as much in bulk or weig-ht, and covers the surface of the field 

 more thickly in the same proportion, the benefit is merely 

 illusory, as the crop does not thus appear to be increased; but 

 if the meaning is, 'that twice the surface is manured as etfect- 

 ually with the same quantity of dung' — then, indeed, we 

 should say that the new plan may be fairly considered as 

 entitled to the most serious consideration. 



The same author, indeed, mentions an instance — cited in 

 Dr. Thomson's System of Chemistry — of an experiment, from 

 which it appears that the periods when putrescent manures 

 begin to produce their eflects, and the length of time during 

 which they continue to operate, are proportioned to the degree 

 of putrefaction under which they are applied. Two pieces of 

 the same kind of soil wore manured — the one with a mixture 

 of dung and straw highly putrefied, the other with the same 

 proportions of dung and straw newly mixed, and the straw 

 almost fre.-h. It was then observed that, during the first year, 

 the plants which grew on the putrefied dung produced a much 

 better crop than the other; but the second year, the ground 

 which had been manured wath the fresh dung produced the 

 best crop: the same result took place in the third year, after 

 which both pieces seemed to be equally exhausted. This, 

 however, only showing that the one was productive of the 

 best crop in the first, and the other in the second year, proves 

 nothing more than an equality of final effect upon the land: 

 upon which it cannot escape reflection, that when the state of 

 the soil does not require progressive improvement, the first 

 crop is generally the main consideration with the farmer ; he 

 naturally, therefore, wishes to place it beyond the reach of 

 those contingencies to which it might be exposed by any 

 deficiency of effective manure. A knowledge of chemical 

 principles, indeed, leads to the inference, that dung ought to 

 be used in a recent state ; and it has been thence assumed, 

 'that any disappointment which, in practice, may have at- 



