PLATE XCV 



Devices for controlling and recording temperatures 



A , Mechanism for shifting the contact on the rheostats controlling the current for 

 heating the outer walls of the calorimeter chamber and the ingoing air. The rheo- 

 stats are almost entirely hidden at the rear of the case inclosing the mechanism. B, 

 Ratio coils for the four bridges governing the action of the shifting mechanism A are 

 combined in this box, together with means for checking the constancy of the resist- 

 ance of the coils and for correcting slight inequalities in them and also to compensate 

 for small differences in the pair of resistance thermometers forming the other arms 

 of each bridge. C, Mechanism for shifting the contact on the rheostat controlling 

 the current in the heating coil in the final heater, shown at E in Plate XCIV. The 

 rheostat is below the case inclosing the shifting mechanism. D, Temperature-differ- 

 ence recorder (self-balancing Wheatstone bridge) for continuously recording the dif- 

 ference between the temperature of the water entering and that leaving the heat 

 absorber. E, "Check box" containing the ratio coils of the bridge for temperature 

 difference measurements and coils for extending the range of differences measured, 

 with means for checking the constancy of the resistances of the coils and the accuracy 

 of the recorder readings and also for compensating for slight differences in the resist- 

 ance of the thermometer coils when they are at the same temperature. 

 42721°— 16 5 



