7 i6 



phate in bones is more valuable than the insoluble phosphate in 

 superphosphates. He may, however, mean that the addition of 

 nitrogen to the superphosphate equalises it with the dissolved 

 bones and that they are then equal ; but this will greatly depend 

 upon what form of nitrogen he is adding. If it is in the form of a 

 nitrate or ammonia salt, he is adding a more valuble nitrogen than 

 that found in dissolved bones, and he would then be comparing 

 the dissolved bones with a superphosphate and a valuable nitro- 

 genous substance and not with a superphosphate alone. It will 

 take more experiments to convince scientitic men that a mineral 

 superphosphate is as valuable a manure as dissolved bones. The 

 following are the experiments made by Professor Maerckcr upon 

 barley in a light sandy soil, very poor in phosphoric acid : 



The next year oats were grown in the pots after the barley, 

 nitrogenous manure being added to each, but no phosphates. Th< 

 following were the results : 



