8 CALORIMETERS FOR STUDYING RESPIRATORY EXCHANGE, ETC. 



desired. Up to the present time it has been unnecessary to utilize this 

 special appliance, as the control by hand regulation has been most satis- 

 factory. 



Two vertical sections through the refrigerating coils are shown in fig. 6. 

 Section A-B shows the entrance near the floor of the calorimeter room. 

 The air is drawn down over the coils, passes through the blower, and is 

 forced back again to the top of the calorimeter room into the large duct. If 

 outdoor air is desired, a special duct can be connected with the system so as 

 to furnish outdoor air to the chamber. This has not as yet been used. 

 Section C-D shows the fan and gives a section through the reheater. The 

 brine coils, 400 meters long, are in triplicate. If one set becomes covered 

 with moisture and is somewhat inefficient, this can be shut off and the 

 other two used. When the frozen moisture melts and drops off, the single 

 coil can be used again. It has been found that the system so installed is 

 most readily controlled. 



The degree of refrigeration is varied in two ways : ( 1 ) the area of brine- 

 coils can be increased or decreased by using one, two, or all three of the 

 coils; or (2) the amount of air passing over the cooling pipes may be varied 

 by changing the speed of the blower. In practice substantially all of the 

 regulation is effected by varying the position of the controlling lever on the 

 regulating rheostat. The apparatus functionates perfectly and the calo- 

 rimeter room can be held at 20 C. day in and day out, whether the tem- 

 perature outdoors is 40 below or 100 above P. 



It can be seen, also, that this system provides a very satisfactory regu- 

 lation of the humidity, for as the air passes over the brine coils the moisture 

 is in large part frozen out. As yet, no hygrometric study has been made 

 of the air conditions over a long period, but the apparatus is sufficiently 

 efficient to insure thorough electrical insulation and absence of leakage in 

 the intricate electrical connections on the calorimeters. 



The calorimeters employ the thermo-electric element with its low poten- 

 tial and a D'Arsonval galvanometer of high sensibility, and in close proximity 

 it is necessary to use the 110-volt current for heating, consequently the 

 highest degree of insulation is necessary to prevent disturbing leakage of 

 current. 



The respiration calorimeter laboratory is so large, the number of assist- 

 ants in the room at any time is (relatively speaking) so small, seldom ex- 

 ceeding ten, and the humidity and temperature are so very thoroughly con- 

 trolled, that as yet it has been entirely unnecessary to utilize even the 

 relatively small amount of indirect ventilation provided in the original 

 plans. 



During the greater part of the winter it is necessary to use only one of 

 the thermostats and the radiators connected with the other can be shut off, 

 since each radiator can be independently closed by the valves on the steam 



