11 
rUESIDENTS AUDIiES«. 
linds matter capable of absorbing the mateiials.” It is probable 
that in the state of chemical science of that day what was thought 
Co be pure air was by no means such. Subsequently to these 
reports of Lavoisier and Thouvenel, another Prench chemist, 
Longchainp, proposed, as a theory, that it was due to the dissolved 
oxygen and nitrogen gases existing in water when mixed with 
calcareous substances that nitrates were produced ; and Professor 
Graham, the late Master of the Mint, and one of the most valuable 
of our past men of research, endorses this view, but supplements it 
by the theory that free carbonic acid known to exist in all ordinary 
water played a very necessary part in the process. At the same 
time, Graham remarks that it cannot be denied that the nitrification 
of calcareous substances is greatly promoted by the contact or 
proximity of putrescent animal and vegetable matter, and the 
constant and universal practice in the formation of artificial nitre 
beds strongly confirms it. Professor Graham goes on to say : 
“ I am disposed to attribute the beneficial effect in nitrification of 
the decomposition of animal and vegetable matter to the plentiful 
supply of an element which exists at all times in the atmosphere 
in perceptible quantity — carbonic acid gas. The free carbonic acid 
renders a portion of the carbonate of lime soluble in the water or 
moisture Avhich must be present, and thereby enables the carbonate 
of lime to act more effectually upon the oxygen and nitrogen which 
the water has absorbed.” In conclusion he says : “ Should this 
theory of the instrumentality of carbonic acid in nitrification be 
eventually substantiated, several improvements in the artificial 
production of nitre might evidently be deduced from it.” 
This was the theory of nitrification up to a very recent date. It 
was well known that certain soils were especially productive of 
nitric acid ; and It became a question of the highest interest to 
scientific agriculturists to ascertain the peculiar circumstances 
under which this important result Avas produced. The theory that 
the soil had power to absorb and appropriate a portion of the 
nitrogen of the atmosphere has been hold, and is, perhaps, still 
hold by some j but there is no proof of this, and the evidence is 
