216 ESSAYS ann OBSERVATIONS 
of perfect quick-lime made of chalk, to 
an exceedingly fubtile powder, by flaking 
it in two drams of diftilled water boiling 
hot, and immediately threw the mixture 
into eighteen ounces of diftilled water in 
a flafk. After fhaking it, a light fedi- 
ment, which floated through the liquor, 
was-allowed to fubfide; and this, when 
collected with the greateft care, and dry- 
ed, weighed, as near as I could guefs, one, 
third ofa grain, The water tafted ftrong- 
ly of the lime, had all the qualities of 
lime-water, and yielded twelve grains of 
precipitate, upon the addition of falt of 
tartar. In repeating this experiment, the 
quantity of fediment was fometimes lefs 
than the above, and fometimes amounted 
to half a grain. It confifted partly of an 
earth which effervefced violently with a- 
qua fortis, and partly of an ochry powder, 
which would not diffolve in that acid. 
The ochry powder, as it ufually appears 
in chalk to the eye, in the form of veins 
running through its fubflance, muft be 
confidered only as an accidental or foreign: 
admixture ;.and, with refpect to the mix 
nute 
