[ *52 ] 
head, he never found that it contained quite fo much 
as half its bulk of this air. If a fufficient quantity 
of quickfilver cannot be procured, oil may be ufed 
with fufficient advantage, for this purpofe, as it im- 
bibes the fixed air very flowly. Fixed air may be 
kept in veffels (landing in water for a long time, if 
they be feparated by a partition of oil, about half an 
inch thick. Pyrmont water made in thefe circum- 
flances, is little or nothing inferior to that which has 
flood in quickfilver. 
The readieji method of preparing this water for 
ufe is to agitate it flrongly with its whole furface ex- 
pofed to the fixed air. By this means alfo, more than 
an equal bulk of air may be communicated to a 
large quantity of water in the fpace of a few mi- 
nutes. Eafy directions for doing this I have publifhed 
in a fmall pamphlet, defigned originally for the ufe 
of feamen in long voyages, on the prefumption that 
it might be of ufe for preventing or curing the fea 
fcurvy, equally with wort, which was recommended 
by Dr. Macbride for this purpofe, on no other ac- 
count than its property of generating fixed air, by 
its fermentation in the flomach. 
Water thus impregnated with fixed air readily 
difiblves iron, as Mr. Lane has diicovered ; fo that if 
a quantity of iron filings be put to it, it prefently 
becomes a flrong chalybeate, and of the mildefl and 
mod agreeable kind. 
I have recommended the ufe of chalk and oil of 
vitriol as the cheapefl. and, upon the whole, 'he bed 
materials for this purpofe ; and whereas fome perfons 
had fufpe&ed that a quantity of the oil of vitriol 
was rendered volatile by this procefs, I examined it 
by 
