PRECAUTIONS TO BE ADOPTED. 41 



stances, the one produces a striking and the other an insensible 

 effect, the lesson to him is clear. In the present condition of 

 his land, he ought to employ the one and reject the other. It 

 matters nothing to him whether the difference arise from the 

 actual scarcity of one of the substances in his land, and the 

 abundance of the other, or from some other cause. To the seeker 

 of the absolute truth it may be of moment, but the profit of the 

 farmer of that given kind of land, in the given condition, is 

 independent of this more refined inquiry. 



2. Precautions to be adopted in making experiments in 

 husbandry. 



Among the precautions to be adopted by the rural experi- 

 menter, the following may be mentioned : 



1. That everything should be done by weight and mea- 

 sure. In field experiments, the land should be accurately 

 measured, and the substances applied, and the produce reaped, 

 exactly weighed. Weight and measure should equally pre- 

 vail in all dairy and feeding experiments ; and on no 

 occasion should any quantity, upon which future proceedings 

 or reasoning is to be based, be guessed at or estimated approxi- 

 mately. 



2. That both the chemical composition and the physical 

 qualities or condition of all substances employed either in feed- 

 ing or in field experiments, should be accurately ascertained 

 and recorded. In all field experiments this should, as much as 

 possible, be the case. In experiments upon feeding, however, 

 a certain latitude may be allowed in the use of vegetable pro- 

 duce such as hay, beans, oats, turnips, &c. of which the 

 average composition may be ascertained, at least approximately, 

 in books upon scientific agriculture. 



3. Two experiments of the same kind, one to check the 

 other, should always be made. In field experiments, the two 

 plots devoted to the same experiment should be as far removed 

 from each other as is convenient, with the view of getting rid 

 of the influence of soil, exposure, &c., which, though unper- 

 ceived, may yet sensibly modify the result of any given appli- 



