Nov. 22, 1915 Improved Respiration Calorimeter 303 



aperture. Several small openings in the walls provide for the passage of 

 air pipes, water pipes, and wires for electric current (PI. XXXII, fig. i). 



The walls, ceiling, and floor of the chamber are of i6-ounce copper, 

 tinned on both sides. Large sheets of copper are used, so that there will 

 be few joints in the walls. The sheets are joined with tightly locked 

 seams heavily soldered, making them air-tight. When the soldering was 

 completed, the tightness of the walls was tested by air pressure, the level 

 of the column of water in a manometer connected with the chamber being 

 observed at frequent intervals for several hours. It remained constant, 

 due allowance being made for the effect of change of temperature or baro- 

 metric pressure during the test. 



The copper-walled chamber is attached to the inside of a framework of 

 structural iron (PL XXXI, fig. 2). The sills and ceiling plates are angle 

 iron with legs about 63 by 63 mm., and are bolted together at the comers. 

 The studding for the side walls and the joists for the floor and the ceiling 

 are of light-weight channel iron about 63 mm. wide, bolted to the plates 

 with stiff angles or elbows, with the width of the channel at right angles to 

 the length of the plates (PI. XXXI, fig. i.) The chamber is attached 

 to the framework by long, slender stove bolts passed through holes in the 

 edge of the channels and screwed into brass nuts soldered to the outer sur- 

 face of the copper. Between each channel and the copper attached to it 

 is a strip of wood about 6 mm. thick and 3.5 cm. wide, to prevent actual 

 metallic contact and to interfere with the transference of heat from the 

 copper wall to its iron supporting structure. Between the copper floor 

 and the floor joists is a layer of asbestos lumber about 9 mm. thick (shown 

 in PI. XXXI, fig. i), to provide a solid support for the thin metal floor of 

 the chamber. 



To the outer edge of the iron structure is attached a surface of sheet 

 zinc corresponding to the copper wall, ceiling, and floor of the chamber 

 (PI. XXXII, fig. i). Sheet zinc about the same weight as that of the 

 copper was used. Washers slipped under the heads of the bolts by which 

 the copper wall is attached serve to bind the zinc to the iron. The cham- 

 ber is thus provided with double metal walls separated by a dead-air 

 space about 7 cm. across, the purpose of which is explained on page 331, 

 in the description of the method of preventing the passage of heat through 

 the walls of the chamber. 



The framework of the chamber was made of structural iron, to secure 

 rigidity and to provide a strong support for any apparatus that it might 

 be found advantageous to employ in experiments in which muscular 

 work would be performed. It entails, however, an undue amount of 

 care in making the calorimetric measurements to avoid error that might 

 result because of the heat capacity and thermal conductivity of the iron, 

 as explained on page 338. Should opportunity to reconstruct the appa- 

 ratus arise, the iron would be replaced by some material that would 

 provide ample rigidity and strength of structure and have less thermal 

 capacity and conductivity. 



