120 A RESPIRATION CALORIMETER. 



As with those on the metal chamber itself, the thermo-electric ele- 

 ments in this system are also subdivided into four sections the top, 

 upper zone, lower zone, and bottom. 



On the chamber itself the different members of each group of ele- 

 ments are permanently connected in series, but with the system here 

 considered it is necessary to break connections in the upper and lower 

 zones when removing the end panels and withdrawing the chamber. 

 The connections between the elements in the top panel and in the bottom 

 panel are in no wise disturbed by withdrawing the metal chamber ; only 

 the wires joining the elements of the upper and lower zones on the side 

 panels with the elements of the upper and lower zones on the end panel 

 must be disconnected. These connections are made by nuts or binding 

 posts. 



GAIN OR Loss OF HEAT THROUGH OPENINGS IN THE CHAMBER. 



The various openings through the metal walls of the chamber have 

 been described in detail (p. 13). The nature of some of these, or at 

 least of the objects for which they are provided, precludes the passage 

 of any appreciable quantity of heat in either direction. In the case of 

 two of them, however, namely, the window in the front and the food 

 aperture in the rear, there is a possibility of gain or loss of heat, de- 

 pending upon differences between the temperature of the air within the 

 chamber and that of the calorimeter laboratory. In fact, that there 

 may be under certain circumstances appreciable interchange of heat 

 through these two openings has been proved by a number of experi- 

 ments in which the temperature of the calorimeter laboratory was 

 markedly different from that of the chamber. To prevent such inter- 

 change of heat it has been found necessary, therefore, to keep the 

 temperature of the laboratory as nearly as possible the same as that 

 within the chamber. 



To this end a mercury thermometer is hung inside the calorimeter 

 chamber with its bulb opposite the center of the window, and a similar 

 thermometer, with exactly the same corrections, is hung outside the 

 window with its bulb at the same level as that of the thermometer 

 inside. It has been found by experiment that when the thermometer 

 on the outside registers exactly the temperature of that on the inside 

 the interchange of heat through the glass is negligible. 



One of the duties of the observer at the table is to record the temper- 

 ature of these thermometers frequently and make such alteration in the 

 heating or cooling of the laboratory as to control the temperature 

 within the necessary limits. Unfortunately the arrangement of the heat- 

 ing system in the building in which the calorimeter is located is such 



