So 6 Mr. Majfey on Saltpetre. 
The ley is then taken out, and fet in a cool place 
for the faltpetre to cryftallize. 
In defed of thefe earths, they colled thofe of 
flables and cow-flails, that have drank up much 
animal urine, the bottoms of ftinking pits and 
ditches, efpecially of thofe, that have received 
the contents of fiaughter and privy houfes. 
Thefe they take out, and lay in heaps, commonly 
mixt up with a little lime, till, by repeated trials, 
they find them fit for their purpofe; which is 
known, in fome meafure, by their having totally 
loft their offenfive odour, a fure fign that their 
putrefadion is completed. 
Where thefe earths cannot be procured in 
fufficient quantities, they form, what are called, 
artificial nitre beds, by laying all forts of putrid 
and putrefiable fubftances in conjundion with 
calcareous earths, keeping them in a moiftftate, 
and waiting, as the phrafe is, till they are 
brought to maturity. If the wood-afhes are not 
added, when thefe materials are committed to 
putrefadion, they are added when they are elixi- 
viated, but never, that we have heard, omitted. 
The common peafants in France and Germany, 
who are almoft all faltpetre makers, ferape toge¬ 
ther the muck and offals of their farm yards, 
and, throwing them under open fheds, fuffer them 
to lie, till they find they will anfwer their end. 
Though they know little of the ufe of putre¬ 
fadion, they take care to promote this procefs, 
by 
