iolent fire, it was converted into a true quick-lime, and had every
other quality of a calcarious earth.

This experiment was repeated with the volatile alkali, and also with the
fossil or alkali of sea-salt, and exactly with the same event.

The third proposition had less appearance of probability than the
foregoing; but, as an accurate experiment was the only test of its
truth, I reduced eight grains of perfect quick-lime made of chalk, to an
exceedingly subtile powder, by slaking it in two drams of distilled
water boiling hot, and immediately threw the mixture into eighteen
ounces of distilled water in a flask. After shaking it, a light
sediment, which floated thro' the liquor, was allowed to subside and
this, when collected with the greatest care, and dryed, weighed, as
nearly as I could guess, one third of a grain. The water tasted strongly
of the lime, had all the qualities of lime-water, and yielded twelve
grains of precipitate, upon the addition of salt of tartar. In repeating
this experiment, the quantity of sediment was sometimes less than the
above, and sometimes amounted to half a grain. It consisted partly of an
earth which effervesced violently with _aqua fortis_, and partly of an
ochry powder, which would not dissolve in that acid. The ochry powder,
as it usually appears in chalk to the eye, in the form of veins running
thro' its substance, must be considered only as an accidental or foreign
admixture; and, with respect to the minute portion of alkaline earth
which composed the remainder of the sediment, it cannot be supposed to
have been originally different from the rest, and incapable, from its
nature, of being converted into quick-lime, or of being dissolved in
water; it seems rather to have consisted of a small part of the chalk in
its mild state, or saturated with air, which had either remained, for
want of a sufficient fire to drive it out entirely, or had been
furnished by the distilled water.

I indeed expected to see a much larger quantity of sediment produced
from the lime, on account of the air which water constantly contains,
and with a view to know whether water retains its air when fully
saturated with lime, a lime-water was made as strong as possible; four
ounces of which were placed under the receiver of an air-pump, together
with four ounces of common water in a vial of the same size; and, upon
exhausting the receiver, without heating the vials, the air arose from
each in nearly the sa