340 
Journal of Agricultural Research 
Vol. V, No. 8 
in the thermometer coils that would result from a change of o.oi degree 
in the temperature of the copper wall. 
The hydrothermal equivalent of the calorimeter has been estimated 
from determinations of the quantity of heat that had to be dissipated 
in the chamber to raise the temperature of the copper wall i degree, and 
the amount of heat that was imparted to the air of the chamber when 
the temperature of the copper wall fell i degree, while the thermal 
conditions of the zinc walls were kept in equilibrium with those of the 
copper wall during the change. The capacity for heat as determined in 
both ways was not far from 40 Calories. From the weights and specific 
heats of the materials entering into the construction of the chamber the 
hydrothermal equivalent was calculated to be between 35 and 40 Calories. 
According to these figures, the quantity of heat in the chamber should be 
increased by 40 Calories with a fall of 1 degree, or decreased by 40 Calories 
with a rise of 1 degree in the temperature of the copper wall, if the thermal 
conditions of the zinc wall were in equilibrium with those of the copper 
wall while the change occurred. 
This will be the case, provided the change in thermal conditions has 
occurred in such manner as to affect the iron supporting structure the 
same as the copper wall. In constructing the calorimeter no provision 
was made for determining the actual temperature of the structure, the 
assumption being that the thermal conditions of the iron framework 
would also be controlled by the regulation of those of the zinc wall, so that 
the temperature of the iron would be quickly brought to that of the 
copper wall and would vary with it. Experience has shown, however, 
that in some circumstances the change in thermal conditions of the iron 
may lag somewhat behind that of the copper wall; hence, it is much more 
desirable to keep the temperature of the walls of the chamber as constant 
as possible for the whole length of an experimental period than to depend 
upon the correction for change in temperature. With a sudden change 
in the rate of dissipation or absorption of heat in the chamber near the 
close of a period, which would affect the temperature of the copper wall, 
there might be an error in the measurement of heat for the period in spite 
of the allowance for temperature change. (See p. 346.) 
Change in Body Temperature op the Subject op an Experiment 
When the human body is the source of heat in the chamber, allowance 
must be made for the heat involved in any change in its temperature, as 
the body has a considerable thermal capacity. From the best available 
data it would appear that a change of 1 degree in the temperature of the 
body involves a change of 0.83 Calorie in the quantity of the heat accumu¬ 
lated for each kilogram of body weight. A rise in body temperature 
would mean that the store of heat in the body has been increased a certain 
amount, which would have to be added to that eliminated by the body 
and measured by the calorimeter during the period in which the rise 
