THE ROTATION OF CROPS. 173 



In all these cases, which seem to militate against a theory 

 perfectly rational in itself, there may be circumstances unde 

 tected or unobserved, which, if known, would fully explain the 

 exception. I do not mean to deny this theory, and certainly not 

 to throw any discredit upon the aid which science may give to 

 agriculture ; but these matters are not so simple as we are dis 

 posed to think them. 



The confidence and presumption of knowledge abate the 

 desire of further attainment, and remove the stimulants to in 

 quiry. Science has yet a great work to perform for agriculture ; 

 and when chemistry can, by analytical examination, show pre 

 cisely what is wanted in any particular soil for the growth of 

 any particular crop, and how it may be supplied, we shall hail 

 the discovery as one of the highest importance, and the noblest, 

 triumph which it can achieve. We believe, at least we con 

 fidently hope, that this may be done. We know what has 

 been promised in this matter, and wait patiently its fulfilment. 

 Agriculture will then be reduced to a system of rules so simple 

 and exact that the plainest mind cannot mistake the course to 

 be pursued. 



At present, we must be guided by practical experience. Most 

 crops are found to diminish in their yield the more frequently 

 they are repeated in immediate succession upon the same land. 

 Manuring for every crop will not always prevent this, although 

 it will commonly do it where an ample supply is to be had. 

 Some crops, it would seem, will bear a repetition much less fre 

 quently than others. Red clover bears to be repeated only once 

 in four or six years, and some farmers would introduce it into 

 the course of crops only once in twelve years ; yet here we are 

 not without dissent, for an experienced and observing farmer 

 says, it may be cultivated as often as we please, provided the soil 

 is sufficiently consolidated. Flax, it is constantly said, cannot 

 be successfully cultivated oftener than once in five years ; yet in 

 one of the counties of New York they cultivate it with advan 

 tage every other year, and the experiment in Ireland has been 

 equally successful. There cannot, however, in spite of these 

 exceptions, remain a doubt, that, in the present state of agricul 

 tural knowledge, there should be an alternation or rotation of 

 crops, as the surest mode of obtaining the largest product from 

 the ground, and of keeping up the condition of the soil. I have 

 15* 



