180 THE PRINCIPLES OF ENGLISH AGRICULTURE. 



judiciously placed enable us to discount those rapid changes 

 in the quality of the soil which sometimes take place within 

 a few yards. In a series of experiments where a large 

 number of various fertilizers are tried, it is of great import- 

 ance not only to have an unmanured plot, but that we 

 should have duplicates and quadruplicates, so that our 

 chain of evidence may be strengthened and brought within 

 the range of strict and immediate comparison instead of a 

 remote comparison with a distant plot on a soil not strictly 

 similar. 



