C 126 ] 
mufl be the foie caufe, that the water receives a tinc- 
ture from galls ; fince, after they are precipitate, it 
lofes that quality, which they notwithftanding retain 
even after they "are feparated from the water. This 
precipitation of the ochrous parts of the water were 
the only vifible effedts that I could perceive to follow 
from the affufion of the ol. tart. p. d. I remember 
indeed, when I was at Moffat, I faw the manufcript 
of Dr. Horfburgh’s experiments upon this mineral 
water ; which appeared to be very accurate ; and 
which I underfhnd are fince printed, in a volume 
lately publiflied by the Philofophical Society at Edin- 
burgh. Amongft thefe I obferved one, which I 
thought fo very remarkable, that I particularly ad- 
verted to it. It was the effedts of the affufion of oh 
tart. p. d. to the water, producing in it clouds, or 
a coagulation of a green or grafs-green colour. I 
think thefe were the words ; and I own I was fome- 
thing furprifed at them. A folution of vitriolum 
Martis, mixed with this alkaline oil, does indeed 
produce a green coagulum : but I could fcarcely 
think, that this, or any other chalybeat water, con- 
tained fo large a proportion of that vitriol, as to be 
fufficient to produce thefe effedts, when I confidered, 
that fo many writers, which I had feen, upon this 
fubjedt, have all failed in their attempts of extradting 
a confpicuous martial vitriol from fuch mineral wa- 
ters. I had tried this experiment upon four or five 
chalybeat fprings in Scotland, and likewife upon the 
Spa and Pyrmont waters, which had been well pre- 
ferved ; but there never refulted any fuch effedts from 
the mixture of thefe with oil of tartar, as are related 
in the above experiment. All the alteration it pro- 
7 duced 
