long as any intermediate ice remained to melt.

Upon these principles, if we conceive a hollow sphere of ice at the
temperature of Zero (32 deg.) placed in an atmosphere 10 deg. (54.5 deg.),
and containing a substance at any degree of temperature above freezing, it
follows, 1st, That the heat of the external atmosphere cannot penetrate
into the internal hollow of the sphere of ice; 2dly, That the heat of
the body placed in the hollow of the sphere cannot penetrate outwards
beyond it, but will be stopped at the internal surface, and continually
employed to melt successive layers of ice, until the temperature of the
body be reduced to Zero (32 deg.), by having all its superabundant caloric
above that temperature carried off by the ice. If the whole water,
formed within the sphere of ice during the reduction of the temperature
of the included body to Zero, be carefully collected, the weight of the
water will be exactly proportional to the quantity of caloric lost by
the body in passing from its original temperature to that of melting
ice; for it is evident that a double quantity of caloric would have
melted twice the quantity of ice; hence the quantity of ice melted is a
very exact measure of the quantity of caloric employed to produce that
effect, and consequently of the quantity lost by the only substance that
could possibly have supplied it.

I have made this supposition of what would take place in a hollow sphere
of ice, for the purpose of more readily explaining the method used in
this species of experiment, which was first conceived by Mr de la Place.
It would be difficult to procure such spheres of ices and inconvenient
to make use of them when got; but, by means of the following apparatus,
we have remedied that defect. I acknowledge the name of Calorimeter,
which I have given it, as derived partly from Greek and partly from
Latin, is in some degree open to criticism; but, in matters of science,
a slight deviation from strict etymology, for the sake of giving
distinctness of idea, is excusable; and I could not derive the name
entirely from Greek without approaching too near to the names of known
instruments employed for other purposes.

The calorimeter is represented in Pl. VI. It is shown in perspective at
Fig. 1. and its interior structure is engraved in Fig. 2. and 3.; the
former being a horizontal, and the latter a perpendicular section. Its
capacity or cavity is divided into three parts, which, for better
di