ter, for instance, remains at
the hundredth part of the height it stood at before the vacuum was
formed, we conclude that one hundredth part of the air originally
contained remained in the balloon, and consequently that only 99/100 of
gas was introduced from the jar into the balloon.

FOOTNOTES:

[58] According to the proportion of 114 to 107, given between the French
and English foot, 28 inches of the French barometer are equal to 29.83
inches of the English. Directions will be found in the appendix for
converting all the French weights and measures used in this work into
corresponding English denominations.--E.

[59] When Fahrenheit's thermometer is employed, the dilatation by each
degree must be smaller, in the proportion of 1 to 2.25, because each
degree of Reaumur's scale contains 2.25 degrees of Fahrenheit; hence we
must divide by 472.5, and finish the rest of the calculation as
above.--E.

CHAP. III.

_Description of the Calorimeter, or Apparatus for measuring Caloric._

The calorimeter, or apparatus for measuring the relative quantities of
heat contained in bodies, was described by Mr de la Place and me in the
Memoirs of the Academy for 1780, p. 355. and from that Essay the
materials of this chapter are extracted.

If, after having cooled any body to the freezing point, it be exposed in
an atmosphere of 25 deg. (88.25 deg.), the body will gradually become
heated, from the surface inwards, till at last it acquire the same
temperature with the surrounding air. But, if a piece of ice be placed
in the same situation, the circumstances are quite different; it does
not approach in the smallest degree towards the temperature of the
circumambient air, but remains constantly at Zero (32 deg.), or the
temperature of melting ice, till the last portion of ice be completely
melted.

This phenomenon is readily explained; as, to melt ice, or reduce it to
water, it requires to be combined with a certain portion of caloric;
the whole caloric attracted from the surrounding bodies, is arrested or
fixed at the surface or external layer of ice which it is employed to
dissolve, and combines with it to form water; the next quantity of
caloric combines with the second layer to dissolve it into water, and so
on successively till the whole ice be dissolved or converted into water
by combination with caloric, the very last atom still remaining at its
former temperature, because the caloric has never penetrated so far as