[ 93 ] 
The water, at the time I ufed it, looked rather foul 
to the eye. On expofing fome of it for a few days 
to the open air, a fcurf was formed on its furface, 
which was nothing elfe but fome of the unneutralized 
earth feparated from the water. - On dropping into it 
a folution of corrofive fublimate, it grew cloudy in a 
fewfeconds; it quickly became opake, and let fall a 
fediment. This is a property, which I believe does 
not take place, in any confiderable degree, in moll of. 
the London waters. 
Experiment I. 
494 ounces of this water were diflilled in a copper 
ftill, till about 150 oz. were drawn off. A good 
deal of earth was precipitated during the diftillation, 
which being colle&ed and dried, weighed 271 
grains. It proved to be entirely a calcareous earth, 
except a fmall part, which was magnefia. This I 
found in the following manner. A little of this earth, 
being mixed with Spirit of fait, diffolved entirely j 
which fhews it to conlift folely of an abforbent earth, 
but does not {hew whether it is a calcareous earth or 
magnefia. The remainder was faturated with oil ot 
vitriol : a great deal of matter remained undiffolved, 
which, as the earth was {hewn to be entirely of the 
abforbent kind, muff have been felenite,or a calcar ious 
earth faturated with the oil of vitriol. The clear liquor 
{trained from off the felenite yielded on evaporation 
only eighteen grains of folid matter, which proved to 
be Epfom fait j fo that all the earth, except that 
contained in the eighteen grains of Epfom fair, muff 
have been of the calcareous kind. That contained mu 
the Epfom fait is well known to be magnefia. 
r The 
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