goz Copy of a Letter, Sc. 
Copy of a Letigr from ‘Tuomas Bepvogs, M.D. Phy- 
fician, at Briftol Hot Wells, to Mr. Tuomas Henry, 
FLR.S. &c. 
READ, NOVEMBER 29, 1793- 
- ae 
Briftol Hot Wells, O&, 17th. 1792, 
DEAR SIR, i ; ‘ be 
if BEG you to communicate, to the Gentlemen of 
your Society, a fact fimilar to thofe related by 
Mr. Willis.* At the bottom of one of Mr. Rey- 
nolds’s {melting furnaces, at Ketley, there was found 
a green, glafly mafs, which, after fome expofure to 
the air, partly deliquefced; and, after a fomewhat 
longer expofure, exhibited white efHorefcences over 
its furface. Thefe efflorefcences I found to confift 
of carbonate of foda. Upon adding diftilled water 
to fome of the recent mafs, and filtering it after- 
wards, I obtained a limpid folution, which, on the 
addition of vitriolic acid, yielded a blue precipitate, 
exactly, as far as L can judge from the defcription, 
of the fame nature, at leaft of the fame appearance, 
as fome of Mr. Willis’s precipitates. The filtered 
folution, probably, contained a triple falt, confilting 
of foda (mineral alkali) iron, and fome third 
material. When the vitriolic acid detached the 
alkali, 
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* Manchefter Memoirs, vol, 4th, part 1ft, page 87, &e. 
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