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On the other hand, the soil is the seat of never-ceasing oxidations, 
caused by the free circulation of air within it; one of these phenomena 
of oxidation is that which acts upon the combustible nitrogenous 
substances held in reserve by the soil; under the simultaneous action 
of a free atmospheric oxygen and of a special kind of microbe, “ the 
nitric ferment,” discovered by Messrs. Schloesing and Miintz and 
described later by Winogradski, these substances are rapidly trans- 
formed into nitrate of calcium, or lime, which, by a happy combina- 
tion of circumstances, is the favorite nutrition of most plants; this 
nitrate of calcium is extremely soluble and does not possess any 
affinity for the elements of the soil, like that existing between these 
same elements and ammonia, or, again, between them and the salts 
of potassium, whence it comes to pass that every infiltration of water 
takes this nitrate along with it, even to the depths of the lower soil, 
and from thence into the brooks, rivers, and thence into the ocean. 
In autumn, when the rains are abundant and when the denuded earth 
evaporates only a small quantity of the water which it receives, a 
veritable cleansing takes place systematically, and all the nitrates are 
carried far away as fast as they are produced. 
The loss from this cause is enormous. In experiments made by 
Messrs. Lawes and Gilbert, at Rothamsted, for a great many years 
past these learned English agronomists have discovered that one 
hectare of soil planted in wheat loses in this w ay 50 kilograms of 
nitrogen—that is to say, as much as the wheat itself contains, or, 
again, a quantity equal to a manuring of 300 kilograms of nitrate of 
soda. 
These figures are far from being exaggerated, and other observers, 
among whom I will mention Deherain, have obtained similar and 
sometimes even higher results than those of Lawes and Gilbert. 
But this is not all. Boussingault found that rich soils continually 
give out ammonia in the gaseous state. These are the circumstances 
under which he discovered it: Having conceived the idea of analyz- 
ing a sample of snow which had remained for thirty-six hones na 
garden bed, Boussingault found in it 10 milligrams of nitric ammonia 
per kilogram, while the same snow taken froma terrace very near there 
contained scar cely 2 milligrams. The difference of 8 milligrams was 
evidently due to the emanations from the earth. If we allow that 
this snow had a uniform depth of 10 centimeters and a mean density 
of 0.25 we shall find on a hectare a total weight of 250 tons, containing 
2 kilograms of ammoniacal nitrogen which was given out from the 
soil during the short time that the snow lay on the | ground. 
‘By what coefficient must we multiply this figure in order to eal- 
culate the amount of annual loss which takes place upon an ordinary 
piece of arable land? We do not know at all, but we can affirm that 
the result of such a calculation would give more than 10 kilograms 
annually per hectare. 
According to Schloesing, certain soils emit nitrogen in its free, 
uncombined state. This is particularly perceptible in soils which 
are badly ventilated and which contain a great deal of organic mat- 
ter. The nitrogen then results from the decomposition of the nitrates 
existing in the soil, which decomposition is attributable, as Deherain 
and I have shown, to the development of certain anerobic micro- 
organisms. 
