Mr. Maffey on Saltpetre. 189 
neutral one, which cryftallizes in the ley when 
boiled down to a due confidence. 
From this plain account of the formation of 
faltpetre, it muft be obvious, that it can no where 
be found, without the concurrence of thefe two 
principles; and, conlequently, not in the air, or 
in vegetables or animals, becaufe, though this 
peculiar acid may, perhaps, be found in thefe 
fubjeds, the fixt fait muft needs be wanting. 
That it may be fometimes found in the earth, 
we fhall not deny, owing to the accidental intro¬ 
duction of wood-afhes to a foil impregnated with 
this acid. And that from hence it may pafs into 
the ftems and apices of fome plants, with the 
moifture that enters their roots, is far from be¬ 
ing improbable. But that whole provinces can 
even be covered over with it, or that it can be 
generated in thefe organized bodies, as Lemeri 
and fome others have imagined, muft exceed 
all belief. 
The accounts, which travellers generally give 
us of this fait, are, that it is extracted from the 
foil of the countries they have vificed, by elixi- 
viating it with water, and evaporating the fluid ; 
which we believe may be confiftent with truth j 
but here it fhould not be forgotten, that a certain 
portion of wood-afhes is always added to this 
foil before it is elixiviated, a circumftance which, 
either through ignorance or inattention they have 
too often omitted to mention. We are told, 
indeed. 
