THE RESPIRATION APPARATUS. 17 



a little below the window opening, and also in figure 32. The water- 

 pipes were embedded in this plug, side by side, about 55 mm. apart, 

 and the orifice sealed with w r ax at the point where the pipes leave the 

 plug inside the chamber. By this means it is possible to have the 

 water current enter and leave the chamber without leakage of water or 

 air. Through the wooden plug also pass two wires used in the meas- 

 urement of the temperature of the incoming air current (p. 122). The 

 openings through which these wires pass are likewise sealed with wax. 



Rod for adjusting position oj shields. In order to raise and lower the 

 aluminum shields of the heat- absorbing system described beyond, a 

 rod passes through the metal walls and connects on the outside with a 

 lever handle shown immediately beneath the window in figure 2, and 

 with a metal quadrant (see fig. 32) to which the phosphor-bronze cables 

 leading to the shields are attached on the inside of the chamber. In 

 order to make the closure through which this rod passes airtight, we 

 rely on a long close telescope-fit between the outside of the steel rod 

 and the inner wall of the brass tube, which is soldered between the two 

 metal walls. As an additional precaution, two or three layers of cotton 

 wicking, well soaked with vaseline, are wound around the steel rod 

 next the copper wall, the pressure of the lever handle on the outside 

 holding the wicking tightly in place. 



Electric-cable tube. The various electric circuits used in temperature 

 measurements and for the telephone are brought together to form a large 

 cable which passes through an opening in the two metal walls, shown 

 in figure 29, a little above the center of the side of the chamber. In 

 this opening, as in the food aperture and wooden plug, a copper tube 

 was soldered to both the zinc and the copper walls. The cable was 

 then inserted and the absolute closure made by coating the space be- 

 tween the cable and both the inside and the outside ends of the copper 

 tube between the two walls with wax. Furthermore, to prevent a leak- 

 age of air through the cable itself (between the strands) , wax was melted 

 into the end of the cable at the point where the wires separate. 



PIPING AND VALVES TO THE BLOWER. 



The air from the chamber passes through the opening A 2 (fig. 33) 

 to the air-pipe leading to the blower. This pipe is of galvanized iron 

 25 mm. in diameter, with ordinary steam fittings and connections. After 

 the piping had been put in place it was subjected to a test of 50 pounds 

 pressure to the square inch. 



The air leaves the chamber, rises through a short length of pipe, 

 and then passes along the ceiling, makes a turn at the corner of the 



2B 



