Ch, VIII.] ON SOILS AND COURSES OF CROPPING. 113 



cannot be extended to an entire farm ; and, after all this, vvlicn the produce 

 is reaped and accurately weighed or measured, the result is calculated 

 according to the exact proportion between the size of the plot on which the 

 experiment was tried, and the square contents of an acre ; though every 

 farmer knows that a material portion of every crop is wasted in the harvest- 

 ing, and that — what with that loss, and the space occupied by headlands 

 and fences — a ten-acre field will hardly yield more than the produce of 

 eight acres estimated in the manner stated. 



Thirdly, even supposing those objections to be obviated — the experiment 

 to be conducted without prejudice, and managed by an intelligent husband- 

 man on the common field plan — still there are so many circumstances of 

 season, soil, and culture, which operate differently at different times, with- 

 out any assignable cause, that what prospers this year fails the next, and 

 what succeeds with one man does not thrive with another. 



Calculations of produce are thus often very fallacious ; and however 

 correct in one situation, are frequently altogether inapplicable to others. 

 Nothing but a series of experiments, and an average of results during many 

 successive years, ought therefore to be considered as decisive of any new 

 practice. Even if found productive, the question may then be fairly asked, 

 at what expense was the produce obtained t And the farmer will find it pecu- 

 liarly jjrudent to look with attention to both sides of the account. The 

 only safe guide is, therefore, to be sought in the practical effects of long 

 continued experience ; but when these coincide with the theories of natu- 

 ralists, they may be safely regarded, if not as unerring rules, at least as 

 being entitled to a considerable share of confidence. 



SOILS. 



The annexed table has been given by Von Thaer as a classification of 

 soils, which we deem entitled to particular attention, as in some degree 

 governing the course of crops ; for, althougli the real value of every rota- 

 tion depends, in a great measure, upon the manner in which its sevei-al 

 processes are executed ; yet, abstractedly speaking, some courses must be 

 viewed as better than others, because the crops may be more suitable to the 

 peculiar qualities of the land on which they are to be grown. The last 

 column in the table comprises an analysis of the comparative value of the 

 different component parts, and is the result of many years' careful examina- 

 tion of the soils, as well as of the proceeds of the crops, after the deduction 

 of labour and seed. 



Nos. 1, 2, and 3 are alluvial soils of the richest quality ; and, from the 

 large portion which they contain of vegetative mould, or humus, and th'j 



