PLATE XXXVI 



Fig. I. — Observer's table: A, Multiple-point switch for connecting electric measur- 

 ing circuits with the galvanometer; B, Wheatstone bridge (temperature indicator) for 

 measuring temperatures of air in the chamber, of the copper walls, and of the body of 

 the subject; C, galvanometer used with the switch and the bridge. The instrument 

 shown here is simply a substitute for a much more sensitive galvanometer which does 

 not appear in this view; D, telephone for communication between the observer outside 

 and the subject inside the chamber; E, push button to call the subject; F, resistance 

 units in series with heating coils outside of zinc wall, as explained on page 336; G, 

 rheostats to control currents for heating zinc walls. 



Fig. 2 . — Devices for regulating temperature of water for heat absorber : A , Preheater, 

 adjusted by hand; B, final heater, adjusted automatically, having an electric heating 

 coil in the bottom and a resistance thermometer coil in the top of the tube; C, bottle 

 filled with pumice, for mixing water flowing from preheater to final heater; D, bottle 

 for mixing water flowing from final heater to heat absorber; E, special cock to regulate 

 rate of flow of v/ater in heater; F, pipe bringing chilled water from cooler to preheater; 

 G, temperature indicator connected with thermometer in final heater; H, needle valves 

 to regulate flow of water to cool air space adjacent to zinc wall ; /, exterior-ends of 

 electric-resistance thermometers in water entering and leaving heat absorber. Leads 

 from these thermometers extend to the bridge marked "G" in Plate XXXV, 

 figure 2. 



