in a cubical foot, and divide the product by the number of cubical
inches contained in the balloon, the quotient is the weight of a cubical
foot of the gas or air submitted to experiment.
Exact account must be kept of the barometrical height and temperature of
the thermometer during the above experiment; and from these the
resulting weight of a cubical foot is easily corrected to the standard
of 28 inches and 10 , as directed in the preceding section. The small
portion of air remaining in the balloon after forming the vacuum must
likewise be attended to, which is easily determined by the barometer
attached to the air-pump. If that barometer, 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
231