16 BULLETIN" 551, IT. S. DEPARTMENT OF AGRICULTURE. 



SUMMARY. 



In this paper there are presented the complete analyses of 45 

 samples of soil, representing four soil provinces. These, together 

 with the analyses of 24 samples previously published representing 

 also four provinces, are discussed from the points of view of extreme 

 variation of all the samples, variation in composition within a soil 

 province, variation of the same type, and the bearing of the limit 

 of error in analysis on the interpretation of analytical data. 



It is thought that the analyses discussed represent nearly the 

 extremes in composition of soils in the regions in which the samples 

 were taken. Marked resemblances in composition of soils from the 

 same province are pointed out. It is shown that some samples of 

 the same type differ considerably in chemical composition. It is also 

 shown that some soils of different types may resemble each other 

 in chemical composition as closely as different samples of the same 

 type. 



It is pointed out that the unavoidable error in analytical operations 

 is in many cases of such magnitude that when analyses are stated in 

 pounds per acre differences of several hundred pounds of some con- 

 stituents are not significant. 



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