Mr. Maffey on Saltpetre . 217 
cf faltpetre. In fo eafy a manner may a nitrous 
earth be prepared. 
We fnall add no more than that the crofter’s 
ley, after it has performed its office of carrying 
off the foul oily parts of linen, or linen yarn, 
and which is generally fuffered to run wafte, 
may here be certainly ufed to good advantage: 
and that we would advife every one who is in¬ 
clined to try experiments, in this way, not to make 
them with lefs than one buffiel of earth, and 
half this quantity of wood-allies, from which two 
gallons of ley may be drawn, which, being 
boiled down to about a pint, may indicate the 
fuccefs, if any is to be expected. 
JP. S. Of the life of Pot-aflo in making of Salt-petre, 
tranflatedfrom the French. 
Thofe who have attended to the former part 
of this work, will, doubtlefs, be fenfible of the 
ufe of wood-affies in the formation of faltpetre. 
That it is impoffible to make this fait without 
them, or fomething of a fimilar nature. Remem¬ 
bering that faltpetre, properly fpeaking, is a 
compofition of two fubftances, united and com¬ 
bined in the fame proportion, which are the 
nitrous acid, and a fixt alkali. 
I hat the faltpetre formed in fome earths, for 
the moll part contains only one of thefe two 
principles ; the nitrous acid, which being com¬ 
bined with a calcareous earth, forms a nitre 
with 
