150 Natural-Philosophical Collections. 
The theory of nitrification is advahted 3 in these terms. 
“ The oxygen and the nitrogen of the atmosphere, led into combination by 
means of the porosity of bodies, and by the presence of water and ofa , 
= to form nitric acid. 
‘ Animal or vegetable matters do not contribute in any degree to the produc- 
tion of nitric acid in nature.” 
And these principles are established upon the following evidence : 
Sect. 1. Nitrates are found formed in materials or places which do not con- 
tain either animal or vegetable bodies, and which have never been under the in- 
fluence of the effluvia of animals. 
Those who have been occupied in the manufacture of saltpetre, are well aware 
that the earth dug out of caves furnishes nitrates by lixiviation, and that this earth, 
after being replaced, will afford, in eight or ten years, additional quantities of 
saltpetre, equal to that which had been before obtained from it. And further, 
after having been again deposited in its former bed, it will again give out salt- 
petre, and that indefinitely, provided that the earth has not been too much robbed 
of the base which favours the formation of nitric acid, and which in nitrifiable 
materials is ordinarily chalk or carbonate of lime; but if there remain nothing 
but clay, nitric acid, not finding a base to saturate itself, will not form. 
Lavoisier has collected, in open quarries, in different places, 40 specimens; 
which for the most part have afforded by lixiviation, a small quantity of saltpetre, 
mixed with much nitrate of lime. 
Thouvenel put two ounces of well washed chalk into a vessel hermetically 
sealed, and containing only atmospheric air. The chalk had been moistened 
with distilled water. In about eight months, he washed it with a lixivium, and 
there subsided six grains of nitrate of lime. And Thovenel adds, (p. 76.) “ Chalk 
afforded nitrous acid in more than fifty different experiments, whether it was res 
newed in each operation, or whether the same chalk. after being well washed, was 
made to serve many times.” 
Hence M. Longchamp draws the conclusion that nitric acid is formed out of 
the elements of the atmosphere, independently of the presence of animal matter. 
Sect. 2. Nitric acid may be formed in the open air, by materials which do 
not contain any vestiges of animal or vegetable matters. 
One of the competitors for the prize of the Academy (page 114 of the cblleciea 
Memoirs) took soil from the fields, and lixiviated it so as to remove all the saline 
particles. He then placed it in a heap, and constantly sprinkled it with pure 
water as it became dry. This soil, on being again lixiviated, in about six months 
furnished saltpetre. 
Another candidate (p. 160) made a still more exact experiment. He took. 
soil from the fields, lixiviated it very completely, and exposed it to the sun. He 
then divided it into two portions, one of which he placed in a cavern upon slabs 
of stone, supported by an iron frame, at a distance of two feet from the walls, and 
as far removed from the floor—the other part was placed upon slabs similarly 
arranged in a coach-house. Both portions were stirred from time to time, and 
BOHN moistened with pure water. At the end ofa year, the gas produced 
by that portion in the cave, after lixivation, was indicated by one degree of the 
aerometer ; the gas from that portion deposited in the coach-house only rose to 
halfa degree. This difference was probably occasioned by the humidity being more 
constantly sustained in the cave than in the coach-house ; but whatever may have 
een its cause, the experiment proves that earth may be nitrified in the air, with- 
Out connection with animal matter. 
Moreover, saltpetre is found in the midst of plains, in all parts of India, in 
Egypt, in Spain, and in many other countries where no animal matter exists. __ 
On his return from the continent of India, Mr. J. Davy stayed at Ceylon, and 
visited the caverns of that island, which produce saltpetre in abundance. In the 
25th volume of the Annales de ‘Chimie, p- 209, the observations will be found, 
from which he arrived at the following’ conclusions : : “ After the examination of the 
