NOV. 32 , 1915 
Improved Respiration Calorimeter 
33 i 
Atwater and Rosa, to prevent gain or loss of heat through the walls, 
though with modifications in details which make the present apparatus 
exceedingly sensitive, while easy to operate. The copper wall 1 of the 
chamber is duplicated by a wall of zinc attached to the outside of the 
iron framework which supports the copper wall, as explained on page 303, 
and the temperature of the zinc wall is regulated to accord with that of 
the copper wall in such manner that the thermal conditions of the two 
walls will be in equilibrium with each other. When the temperature of 
the zinc wall is the same as that of the copper wall, the quantity of heat 
transmitted from each wall to the other is the same, so that neither wall 
actually gains heat from the other. The effect of such a condition on 
the quantity of heat in the chamber would be the same as if no heat were 
to pass from either wall to the other in either direction. If the tempera¬ 
ture of the zinc wall is above that of the copper wall, the quantity of 
heat passing from the zinc to the copper is greater than that in the reverse 
direction—i. e., the copper wall will gain heat from the zinc wall, some 
of which, at least, it will transmit to the air of the chamber. Con¬ 
versely, if the temperature of the zinc wall is below that of the copper 
wall, the former will gain heat from the latter, some or all of which the 
copper wall has derived from the air of the chamber. If the quantity of 
heat which the copper wall has gained from the zinc wall is counter¬ 
balanced by an equal quantity gained by the zinc wall from the copper 
wall, the effect on the measurement of the quantity of heat produced in 
the chamber is the same as if no heat had been transferred from either 
wall to the other. This counterbalancing may be accomplished by 
keeping the temperature of the zinc wall above or below that of the 
copper wall, as need be, to the same degree and for the same length of 
time that the conditions were reversed. Tor this purpose means are 
provided for determining when the zinc wall is warmer or colder than the 
copper wall, and for heating and cooling the zinc wall as is found necessary. 
Detecting Differences in Temperature of the Double Metal Walls 
Thermoelectric thermometers are used to detect any difference between 
the temperature of the zinc wall and that of the copper wall. Differential 
thermoelements are installed between the two walls, with the junctions 
at one end of each element close to the outer surface of the copper wall, 
while those of the other end are in the plane of the zinc wall, and the 
terminals of the elements are connected with a sensitive galvanometer. 
The direction of the deflection of the galvanometer indicates whether the 
zinc wall is warmer or cooler than the copper wall—i. e., whether to 
warm or to cool the zinc wall. 
Each thermoelement consists of four copper-constantan couples made of 
bare hard-drawn wire about 1 mm. in diameter (No. 18, American gauge). 
In making the junctions, the copper and constantan wires were put end 
1 As used in this section, the term “wall'’ may include the ceiling and the door as well as the sidewalls. 
9841°—15 - 3 
