WITH QUICKLIME APPLIED ALONE. 231 



with the expense of the application. But lime is not so immediate 

 in its action upon corn as upon green crops, and its full influence 

 only becomes perceptible after a series of years. This experi- 

 ment of Mr Caird's ought, therefore, to have been continued the 

 crops on the several acres being weighed during the succeeding 

 four or five years. In this way only can the true effects, econo- 

 mical and theoretical, of lime be made out, and data be obtained 

 on which we can safely reason and rely. Time and trouble, it is 

 true, are involved in such prolonged experiments, and we ought 

 not perhaps to expect them from purely practical men, who, in 

 our country, are generally rent-paying farmers. But they 

 must and will be made, as individuals and societies become 

 impressed with clearer views of the precise position in which 

 scientific agriculture now stands. 



I may draw the attention of the reader to the illustration 

 which this experiment of Mr Caird's affords of the varying 

 produce of different portions of the same field, considered 

 uniform in quality throughout. The three unlimed acres 

 yielded of grain 44, 40, and 43 bushels respectively, being a 

 difference of 4 bushels, or 10 per cent, between the first and 

 second unlimed acres. We are unable to compare the diffe- 

 rences in the produce of straw. On the almost universal occur- 

 rence of such natural differences I have elsewhere insisted, 

 (p. 48.) Almost every new series of comparative results we 

 examine enforces more the necessity of duplicate or triplicate 

 trials, if we would obtain numerical results, on which reliance 

 can be placed. 



g Q t Suggestions for experiments with silicate of lime, and with 

 burned limes which contain it. 



I have shown in a preceding section that burned limes differ 

 chiefly in the proportions of siliceous or earthy matter, of 

 magnesia, and of phosphate of lime, which they severally con- 

 tain. It is desirable, not merely for the purpose of testing 

 theoretical views, but with a view to the economical benefit of 

 those districts in which different kinds of lime are within the 

 reach of the farmer, that precise experiments, with the view of 

 testing the special effects of each, and their comparative values 



