EQUIVALENT PKOPOKTIONS. 



117 



substances will be strictly comparative. This is a point never 

 hitherto taken into account in agricultural experiments, but it 

 is one of great scientific importance. 



In all such comparative experiments, therefore, with these 

 substances, we ought to employ 



Against 100 Ib. of sulphate of potash, 



82 Ib. of dry sulphate of soda, 

 or 184 Ib. of crystallised sulphate of soda. 



