freezing point of water. This fuppoiition ftaggered the faith of
many philofophers, and made them anxious that the matter fhould
be more fully inveitigated. Accordingly the Royal Society of
London defired its members refiding in cold countries to turn
their attention towards determining the point of congelation of
mercury, and to remark the defcent of the mercury in the thermometer
during the procefs from the freezing point of water to
that of mercury, in order to form a jufter notion of the real
contraction of that metal. But it was not till lately that light
was thrown on the fubjeCt, by a courie of experiments made at the
defire of the Royal Society, by Mr. Hutchins, governor of Hud-
fon’s Bay, who received excellent inftruCtions from Mr. Caven-
diih, and Dr. Black, profelfor of cliemiftry in the univerfity of
Edinburgh. Thefe directions, and an apparatus made in London
for the purpoie, enabled the governor to perceive, that the
fudden and confiderable defcent which takes place in the lower
parts of the thermometer, when expofed to great cold, happens
from the contraction of the metal in its frozen Rate, and does not
affeCt the regularity and juitnefs of its contraction whilil it reremains
fluid. This great point was principally afcertained by
means of a fpirit thermometer, which was found not to freeze as
foon as the mercury, arid thereby indicated the degree of cold
produced by his frigorific mixture, when the mercurial thermometer
ceafed to roeafure it on account of its contraction on becoming
folid.
In order to prove, that the defcent of the mercury in the thermometer