igo Mr. Majfey on Saltpetre. 
indeed, by Mr. Bowles, that in Tome parts of 
Spain, they have an earth that yields the cryf- 
tals of this fait without any afliftance of this 
kind ; and this in fuch quantities, as might fupply 
all Europe with this article. But till this fa<ft is 
better authenticated, we have many reafons to 
doubt the truth of it. 
Be this as it may, we (hall here judge it of more 
life, to advert to thofe earths, that are well known, 
with the afiiftance of wood afhes, to yield us the 
cryftals of this fait, to point out their peculiar 
quality, and the fource from which it is derived ; 
together with the true reafon why they are not 
always in a condition to yield us thefe cryftals, 
even with the addition of a fixt fait; a circum- 
ftance that has much perplexed the molt expe¬ 
rienced faltpetre makers. After which, nothing 
we truft will remain, but to lay down the prac¬ 
tical methods of making it, fupported by the 
bed authorities, as well as our own experience. 
Of thefe earths, the mod diftinguifhed are, the 
rubbifh of old houfes, the ruins of old vaults 
and cellars, &c. which rarely fail to yield us 
the cryftals of this fait, when elixiviated with 
wood afhes. That thefe earths poffefs an acid 
quality, is not to be difputedj feeing, that 
upon reducing them to a coarfe powder, and 
percolating a fixt alkaline folution through them, 
this folution will be neutralized, and no longer 
yield us an alkaline, but a neutral fait. 
From 
