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JOHN K. MURLIN 



the observer who reads the electrical variations on the Wheatstone bridge, 

 so that the amount of current flowing through the several "parts" is under 

 accurate control. Any tendency for heat to pass outward would be indi- 

 cated by a deflection of the galvanometer showing that the zinc wall was 

 cooler than the copper. Such an indication, however, would be immediately 

 checked by turning additional current into the heating wire, thus restoring 

 the temperature of the zinc wall to that of the copper wall and thereby 

 preventing escape of heat. 



The interior of the chamber is so arranged as to give the utmost com- 

 fort to the subject. It is obvious that if the heat were not carried away 



Fig. 27. The wiring- diagram of the observer's table with the Sage calorimeter. 

 In the center is the Kohlrausch bridge, to the right a tapping key with an arrange- 

 ment for throwing in 300 ohms resistance when needed. This key is used in reading 

 the thermopiles connected with the switch on the right. To the left of the bridge 

 is a switch for connecting either thermopiles or resistance thermometers with the 

 galvanometer. On the extreme left is the switch for the air, wall, rectal, ingoing and 

 outgoing water thermometers, each of which contains 100 ohms. 



from so confined a space the temperature would very shortly become un- 

 bearable. The heat absorbing apparatus is installed on the ceiling of the 

 chamber. In the later constructions this absorber consists merely of a 

 continuous grid of copper pipes covering the entire ceiling. In the Cornell 

 and Sage calorimeters the temperature of the water as it enters is brought 

 to the desired level by means of a Gouy temperature regulator. This device 

 insures great constancy in the temperature of the water. With the speed 

 of the water current properly regulated and its temperature brought to 

 a constant level as it enters the apparatus fluctuations in the heat pro- 

 duction will be manifested by fluctuations in the temperature of the water 

 as it leaves the chamber. Extreme variation in the former, however, re- 

 quires readjustment, of both speed and temperature of entering water. 



After circulating through the heat absorber the water is caught in a 



