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anfwcred my expectation. It is found either in round 
or broad pieces, is exceeding ponderous, and of a 
Ihining yellow colour, and is called by the miners 
braj\ lumps. When I infufed this mineral for a fhort 
time in common water, it communicated to it all 
the properties of a fteel Spaw ; its tafle was exactly 
the fame ; and it received a tindure from galls, which 
was of a more diluted or intenfe purple, according 
to the proportion of the mineral added to the water, 
or to the time of the infufion. This Ample experi- 
ment does therefore clearly difcover to us the origin 
of fteel waters, and the manner, in which they are 
impregnated with their mineral contents in the bowels 
of the earth. 
This obfervation, which I had made concerning 
the origin of fteel waters, led me, when I firft vifited 
Hartfell-Spaw, to inquire into the adjacent foffils : 
which was the more eafily done, as the ftrata of the 
earth about the well, for a confiderable depth, are 
expofed to view. After fome fearch among thefe, I 
found a ftratum of cliffery rock, about three or four 
feet thick, of a grey colour, and, I think, about 
twenty paces from the fpring. In fome of the hol- 
low places of this rock, where the rain and wind 
did not reach, I obferved a white faline efflorefcence 
on its furface, which when I had taken off and 
tailed, I concluded, from its ftyptic and chalybeat 
tafte, that it was a native vitriolum Martis, not- 
withftanding its white colour ; but I found it, upon 
trial, to be alum, having fome fine attenuated parts 
of iron conjoined with it, and the fame fait with that 
contained in the Spaw water. 
Having 
