I % e J 
Mr. Majfey on Saltpetre. 
many that, in a due courfe of time, might have 
anfwered their moft fanguine expectations. 
d hey have, likewise, not duly attended to the 
large quantities of earth, that our neighbours are 
obliged to elixiviate, in order to obtain a final! 
portion of faltpetre; and finding their portion but 
trifling in the trials they have made, have too 
haftily concluded this bufinefs to be fcarcely worth 
following ; when, had they reflected upon the 
great number of faltpetre-makers in France and 
Germany, they muft, certainly, have entertained 
a very different opinion. 
But what has chiefly difeouraged us, we pre¬ 
fume, may have been, our ignorance of the true 
grounds and principles, upon which the practice 
of making faltpetre is founded; which, we 
may obferve, have never been clearly laid open. 
All that we are told is, that faltpetre is extracted 
from the rubbifh of old houfes, the bottoms of 
/linking pits and ditches, and the like; which 
has induced many perfons to conclude, that this 
fait is generated in thefe earths: whereas, the 
truth is, that nothing is extracted from thefe 
earths but a peculiar acid, which, in con¬ 
junction with the fixt fait of wood-afhes, and not 
yvithout, forms this neutral one which cryftallizes 
in the ley when boiled down as above mentioned ; 
which circumftances being omitted, it can be no 
wonder that we are led into very great errors. 
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