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Scotland or elfewhere, that afforded an intenfe black 
and inky colour with galls. From which, I think 
we may venture to conclude, that the water of this 
Spaw contains a far larger proportion of iron than 
moft, or perhaps than any, other chalybeat water 
hitherto difcovered : and for this reafon, I dare fay, 
it will likewife be fo much the more preferable to 
moft others in medicinal virtues ; which has indeed 
already appeared by many lurprifing cures it has 
performed, and which, I am perfuaded, will more 
fully appear, when its medicinal effedts ftiall be 
better known. 
There muft needs be a very great quantity of iron 
in this water, when it yields as deep a colour with 
galls as a ftrong folution of fal Martis. I was indeed 
at firft apprehenfive, that this perhaps might not be 
owing fo much to a large and uncommon proportion 
of chalybeat parts, as to the commixture of alum, 
which I judged to be in the water. But we fee the 
contrary appears by thefe trials : for alum of itfelf 
affords no tindture with aftringents, and, inftead of 
rendering a folution of fal Martis with galls of a more 
intenfe colour, rather makes it lighter and more di- 
luted. 
We fee here, that the ferrugineous matter is intirely 
feparated from the water by an infulion of galls. 
The like alfo happens by elixation ; after which it is 
almoft deprived of its tinging quality. Yet other 
chalybeat waters lofe this quality by a much lefs de- 
gree of beat. 
As there is an ochrous earth Separated from all 
fteel waters, when expofed to the air, which fubftdes 
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