INFLUENCE OF TEMPEKATURE. 



71 



1845. 

 Inches. 



1846. 

 Inches. 



1847. 

 Inches. 



1848. 

 Inches. 



27-20 32-64 20-38 37'20* 



The annual fall of rain here ranges from 20 inches, in 1847, 

 to 37 inches in 1848, and the variations in the several months 

 are in nearly equal proportion. Such diversities, whether local 

 or general, must occasion similar differences in the results of 

 experiments made with the same substances, in similar circum- 

 stances, in different years ; and it is especially to be remarked, 

 that saline applications in very dry years may do harm instead 

 of good diminishing instead of increasing the crop. 



I need scarcely allude to the influence of diversities in the 

 temperature of the air, and of the soil, as necessary sources of 

 dissimilarity among results obtained in circumstances otherwise 

 analogous. The comparative warmth of a season will obviously 

 affect our experiments, not less than its degree of humidity. 

 But, independent of season altogether, as a wet soil is colder 

 than a dry one of the same kind, and as the air on a higher is 

 colder than on a lower elevation, a difference in regard to these 

 circumstances may in the same season cause the same substances 

 to produce unlike effects upon similar crops. The careful sifter 

 of experiments must bear all such things in mind, in comparing 

 results, and in attempting to reconcile such as differ, or to extract 

 general rules and principles from such as agree. 



The maker of experiments, also, must neither be surprised 

 nor discouraged if a series of trials which has cost him thought, 



* Gardeners' Chronicle, March 31, 1849, p. 198. 



