stinction, I shall name the interior, middle, and external cavities.
The interior cavity f f f f, Fig. 4. into which the substances
submitted to experiment are put, is composed of a grating or cage of
iron wire, supported by several iron bars; its opening or mouth LM, is
covered by the lid HG, of the same materials. The middle cavity b b b
b, Fig. 2. and 3. is intended to contain the ice which surrounds the
interior cavity, and which is to be melted by the caloric of the
substance employed in the experiment. The ice is supported by the grate
m m at the bottom of the cavity, under which is placed the sieve n
n. These two are represented separately in Fig. 5. and 6.

In proportion as the ice contained in the middle cavity is melted, by
the caloric disengaged from the body placed in the interior cavity, the
water runs through the grate and sieve, and falls through the conical
funnel c c d, Fig. 3. and tube x y, into the receiver F, Fig. 1.
This water may be retained or let out at pleasure, by means of the
stop-cock u. The external cavity a a a a, Fig. 2. and 3. is filled
with ice, to prevent any effect upon the ice in the middle cavity from
the heat of the surrounding air, and the water produced from it is
carried off through the pipe ST, which shuts by means of the stop-cock
r. The whole machine is covered by the lid FF, Fig. 7. made of tin
painted with oil colour, to prevent rust.

When this machine is to be employed, the middle cavity b b b b, Fig.
2. and 3., the lid GH, Fig. 4. of the interior cavity, the external
cavity a a a a, Fig. 2. and 3. and the general lid FF, Fig. 7. are all
filled with pounded ice, well rammed, so that no void spaces remain, and
the ice of the middle cavity is allowed to drain. The machine is then
opened, and the substance submitted to experiment being placed in the
interior cavity, it is instantly closed. After waiting till the included
body is completely cooled to the freezing point, and the whole melted
ice has drained from the middle cavity, the water collected in the
vessel F, Fig. 1. is accurately weighed. The weight of the water
produced during the experiment is an exact measure of the caloric
disengaged during the cooling of the included body, as this substance is
evidently in a similar situation with the one formerly mentioned as
included in a hollow sphere of ice; the whole caloric disengaged is
stopped by the ice in the middle cavity, and that ice is preserved from
being affected