[ *44 ] 
they fuppofe, that it is firft imbued with an acid in 
the bowels of the earth ; and then, by the corrofion 
of the chalybeat minerals, thro’ which it runs, it 
comes to.be impregnated with them. I once re- 
ceived this opinion, as the moft probable I could 
then obferve, concerning the origin of thefe fprings : 
yet not as being fatisfaCtory ; for there are many ob- 
jections againft it, which it is difficult either to elude 
or to anfwer. 
The fuppoffiion of an acidity in ferrugineous wa- 
ters, I thought but ill confirmed, becaufe, upon trial, 
they difcover no veftiges of it, but rather appear to 
be alkaline. Befides, in coniidering the caufes of 
mineral waters, it feems more probable, that what- 
ever minerals they contain, they muft be fuch, as can 
be received or extracted by common water in its 
paffiage thro’ the earth, by folution, abrafion, or the 
like iimple operations j and in this way alone I 
think we may come to account not only for the 
commixtion of the faline and terrene minerals, which 
are found in medical waters, but likewife of thole, 
that are metalline or fulphureous ; for which Iimple 
water, at firft fight, may perhaps feem to be an in- 
fufficient folvent. 
It was this notion, that firft induced me to make trial 
upon various mineral and metallic bodies, in order to 
know how far they could communicate their virtues 
to common water by infufion. I thought this might 
throw fome light upon the origin of mineral waters : 
yet, tho’ I made a great many experiments of this 
fort, and particularly upon feveral kinds of native 
chalybeat minerals, I was as little fatisfied concern- 
ing their origin as before. I at length, however, 
met, 
