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 water 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; 7 , exterior ends of 
electric-resistance thermometers in water entering and leaving heat absorbef. Leads 
from these thermometers extend to the bridge marked “G" in Plate XXXV, 
figure 2. 
