al loss of heat. The
calorimeter is surrounded by an air-jacket connected to a petroleum
gauge which indicates any small change of temperature in the
calorimeter, and enables the manipulator to adjust the supply of cold
water to compensate it. The apparatus as arranged by F.A. Waterman is
shown in fig. 1 (_Physical Review_, 1896, iv. p. 161). A is the
calorimetric tube, B the air-jacket and L the gauge. H is an electric
heater for raising the body to a suitable temperature, which can swing
into place directly over the calorimeter. W is a conical can
containing water cooled by ice I nearly to 0 deg., which is swung over
the calorimeter as soon as the hot body has been introduced and the
heater removed. The cold water flow is regulated by a tap S with a
long handle O, and its temperature is taken by a delicate thermometer
with its bulb at G. The method is interesting, but the manipulations
and observations involved are more troublesome than with the ordinary
type of calorimeter, and it may be doubted whether any advantage is
gained in accuracy.

[Illustration: Fig. 2.]

The _continuous flow method_ is specially applicable to the important
case of calorific value of gaseous fuel, where a large quantity of
heat is continuously generated at a nearly uniform rate by combustion.
Fig. 2 illustrates a recent type of gas calorimeter devised by C.V.
Boys (_Proc. R.S._, 1906, A. 77, p. 122). The heated products of
combustion from the burner B impinge on a metal box H, through which
water is circulating, and then pass downwards and outwards through a
spiral cooler which reduces them practically to the atmospheric
temperature. A steady stream of water enters the apparatus by the
inflow thermometer O, flows through the spiral coolers N and M, and
finally through the box H, where it is well mixed before passing the
outflow thermometer P. As soon as a steady state is reached, the
difference of temperature between the outflow and inflow thermometers,
multiplied by the current of water in grammes per minute gives the
heat per minute supplied by combustion. The gas current is
simultaneously observed by a suitable meter, which, with subsidiary
corrections for pressure, temperature, &c., gives the necessary data
for deducing calorific value.

A continuous flow calorimeter has been used by the writer for
measuring quantities of heat conveyed by conduction (see CONDUC