THE CALORIMETER SYSTEM AND MEASUREMENT OP HEAT. 137 



within the chamber, pass out through a groove in the under side of the 

 circular wooden plug projecting from the wooden walls at the left of 

 the table and terminate in the mercury switch at the rear of the center 

 of the table. This switch is described in detail beyond. 



The electrical connections for the heating systems in the different 

 sections of the air-spaces are made through the rheostat at the rear 

 of the left end of the observer's table. Inasmuch as there are eight 

 sections of the air-spaces, and one resistance lamp is used to vary the 

 temperature of the incoming air, the rheostat has nine sections, each of 

 which is connected, by means of a cable passing through the floor of the 

 platform (seen under the table in fig. 37), with its resistance coil lying 

 between the respiration chamber and the floor, as explained on page 1 18. 



The flow of water through the pipes for cooling the different sections 

 of the air-spaces, and through the pipe for cooling the ingoing air, is 

 regulated by the ten valves immediately above the rheostat. The upper 

 four valves control the four sections of the inner air-space, the four 

 immediately beneath them those of the outer air-space, and the fifth 

 valve on the lower line, the circuit for coolingthe ingoing air. The valve 

 at the extreme left is used to maintain a constant flow of water into the 

 supply tank in another part of the building. (See p. 126.) At the right 

 of the table* are several resistance coils, and upon the table a portable 

 voltmeter, used in electrical check experiments. (See p. 169.) 



The millimeter scale on which the deflections of the galvanometer are 

 read is immediately in front of a small clock on the black-cloth hood 

 in which the galvanometer is placed. The two upright thermometers 

 inserted in the wooden plug at the left of the observer's table indicate 

 the temperatures of the ingoing and outcoming water for the heat- 

 absorbing system. A little below and at one side is seen the lever for 

 raising or lowering the shields to the heat-absorbers inside the chamber. 

 This moves over a graduated arc into which a peg on the handle fits, 

 thus allowing for fine adjustments. Of the three small switches under 

 the edge of the table, at the left, one completes the telephone circuit 

 to the chamber and the others are for connections with the bicycle 

 ergometer (see p. 164) and with electrical devices used within the cham- 

 ber in electrical check experiments. 



The water-meter, which is not shown in figure 37, stands on the floor 

 immediately at the right of the observer, as it appears in figure 3. 

 Thus it is seen that from the position of his chair the observer can note 

 through the glass door the movements of the subject inside the chamber, 

 read the mercurial thermometers in the water-cooling circuit, heat or 

 cool various sections of the chamber, raise or lower the shields, note 

 temperature differences on the galvanometer, and note the quantity of 

 water passing through the water-meter. 



