I'KES 1 U EN t’« a L) D RESi^. 
13 
many experiments were undertaken in order to understand the true 
theory of the process. 
iJefore describing any of tliese theories, however, 1 may say that 
tl>e practice of making artificial nitre was largely carried on in 
k'rance, Germany, Switzerland, ami Sweden. In this latter country, 
indeed, a law was passed that every landed proprietor should be 
bound to supply a certain proportion of nitre according to the 
extent of his possessions. And in all cases it was found that the 
best conditions for the j)roduction of nitre Avere a loose porous earth 
containing lime, magnesia, potash, etc., the beds being mainly 
composed of old building rubbish, marl, morter, chalk, with a 
mixture of ordinary soil and decaying organic nitrogenous substiinces. 
The presence of moisture and a free current of air was absolutely 
necessary, and a temperature of not less than G0° or 70° Fahrenheit. 
Glauber, one of the fathers in chemistiy, laid it down as an 
axiom, tliat “saltpetre was formed by the decomposition of animal 
and vegetable sul)stances.” This theory Avas hotly contested by 
Lavoisier and Thouvcncl. Tlic former chemist found abundant 
evidence of the existence of nitrates in specimens of chalk from 
Koche Guyon and Mousseux. These specimens Avere taken from 
])laces a long Avay removed from all habitations, and from parts of 
the rock exposed to rain and all vicissitudes of the Aveather ; and he 
came to the conclusion “ that nitric acid does not pre-exist in this 
chalk, but is formed by tiie action of the air.” The <|uantity of 
nitre Avhich any specimen contained Avas found to depend most upon 
its vicinity to the surface. ThouA^enel produced nitrates by exposing 
chalk to the gases evolved from the putrefaction of animal and 
vegetable substances mixed Avith common air; and he likeAvise 
obtainevl them Avhen the same kind of chalk AA'as in contact Avith 
nothing but atmospheric air. It is true he obtained nearly three 
times as much from tlic experiment in the presence of jnitrefying 
gaseous matter as he did from the alleged pure air ; nevertheless he 
concludes: “ It is demonstrated by these experiments that atmos- 
pheric air possesses all that is necessary to serve for nitrification as 
Avcll as the air Avhich emanates from putrescent bodies, provided it 
