338 TiMEHRi. 
organism is so abundant that it is rare to find a particle 
of arable soil that is not effective in causing the conver- 
sion of ammonia into nitric acid. 
Although no experiments have been made to decide 
the point, yet, it is to be expected that the waste of 
nitrogen that occurs when ammoniacal salts are used as 
manure, would approach its maximum in a country like 
British Guiana, where the rainfall is so constant and 
abundant, and the prevailing temperature not far 
removed from that at which the greatest activity is mani- 
fested by the nitrifying organism. 
It was LlEBIG who first suggested the addition of sul- 
phuric acid to ground bones used as manure to render 
them soluble in water and thus capable of more readily 
supplying plants with the phosphorus they require. The 
manufacturers carry out the suggestion by simply adding 
from 25 to 50 per cent, of sulphuric acid to bone or 
other phosphate, which is then, after a certain interval 
to allow of the action of the acid being complete, sold 
as superphosphate or " soluble" phosphate of lime at 
an increase of at least 75 per cent, on the value of the 
substance thus made soluble. Excellent results have 
frequently attended the application of this soluble prepa- 
ration to root crops in Europe, but, on the other hand, 
instances are not wanting in which it has failed to 
realise the expectations formed of it, by showing the 
marked advantage over ordinary insoluble phosphate 
commensurate with its increased cost. In soils contain- 
ing much lime or chalk, it is obvious that it must quickly 
revert to its original insoluble condition by the neutrali- 
zation of the acid with which it is associated ; whilst in soils 
containing ferric oxide, hydrate, or what is perhaps less 
