For use in measuring the temperature of the air and of the copper wall of the calorimeters, as well as the rectal temperature of the subject, a series of resistance thermometers is employed. These are so connected on the observer's table that they may be brought into connection with two Wheatstone bridges, W_{1} and W_{2}. Bridge W_{1} is used for the resistance thermometers indicating the temperature of the wall and the air. Bridge W_{2} is for the rectal thermometer. Since similar thermometers are inserted in both calorimeters, it is necessary to introduce some switch to connect either set at will and hence the double-throw switches S_{1}, S_{2}, and S_{3} allow the use of either the wall, air, or rectal thermometer on either the bed or chair calorimeter at will. Since the bridge W_{1} is used for measuring the temperature of both the wall and the air, a fourth double-pole switch, S_{4}, is used to connect the air and wall thermometers alternately. The double-contact key, K_{1}, is connected with the bridge W_{1} and is so arranged that the battery circuit is first made and subsequently the galvanometer circuit. A similar arrangement in K_{2} controls the connections for the bridge W_{2}. GALVANOMETER. The galvanometer is of the Deprez-d'Arsonval type and is extremely sensitive. The sensitiveness is so great that it is desirable to introduce a resistance of some 500 ohms into the thermal-junction circuits. This is indicated at the top of the diagram near the galvanometer. The maximum sensitiveness of the galvanometer is retained when the connection is made with the Wheatstone bridges. The galvanometer is suspended from the ceiling of the calorimeter laboratory and is free from vibration. RESISTANCE FOR HEATING COILS.