1902.] PUBLIC DOCUMENT — No. 33. 109 



It must be understood that the chemical character of many 

 of the refuse substances used for manurial purposes is con- 

 stantly undergoing changes, due to frequent variations in 

 the parent industry. 



As a rule, in all succeeding analyses the essential con- 

 stituents are determined and stated ; blanks do not imply 

 the absence of the non-essentials. 



