MEMOIR ON THE ORIGIN OF NITRE. 343 
3. That it is not formed by the oxydation of the nitrogen 
of ammoniacal gas or of organic matters, at the expense of 
the oxygen of the air. 
4. That, finally, it is formed only when nitrogen is found 
in presence of an excess of oxygen, that is to say, in a case 
which does not ordinarily occur in nature. 
These conclusions, adds the author, will receive further 
confirmation in the second part of this work, which will be 
devoted to showing how the nitrification of stones is pro- 
duced . — Comptes Bendus , No. 2, July 14, 1856. 
SECOND PART. 
An attentive study of the causes of nitrification has 
shown me : 
1. That it is produced in all porous bodies, of whatever 
nature; thus rotten-stone, plaster, chalk, brick, freestone, 
sand, wood, and charcoal, are susceptible of being charged 
with nitre when they are placed in favorable conditions. 
2. That in walls, the nitrified portions are entirely dis- 
tinct from those which are not so. 
3. That they exhibit very clearly defined stains, sometimes 
of great extent in ancient constructions, and differing con- 
siderably in colour from the stains of simple moisture, which 
are not nitrous. 
4. That these stains proceed ordinarily from the privies, 
or places into which the liquids which escape from them 
pass by infiltration. 
5. Finally, that in pigeon-houses and poultry-houses, 
where there is no escape of fluid, and where, nevertheless, 
powerfully ammoniacal vapours are disengaged, the walls are 
nitrous only when they are sufficiently raised from the soil. 
It evidently resulted from the whole of these facts, that 
nitrification is not produced by a gaseous emanation, but 
only by the progressive imbibition of a liquid ; now, as urine 
is the liquid which most ordinarily escapes from privies, and 
as, moreover, I have ascertained that it is sufficient of itself 
for producing the nitrification of walls, it followed naturally, 
that it was the principal, if not the only cause of nitrification. 
The question was then reduced, in fact, to determining how 
it is produced. The long and tedious researches to which I 
devoted myself, with this view, led me to this unexpected 
conclusion, that animals have not the power of forming nitric 
acid, and that the nitre which is found in their urine is 
foreign nitre. It was necessary now to ascertain the source 
from which they derive it ; vegetables naturally appeared to 
me to be the source. 
