To bring away the heat produced by the subject, it is highly desirable that a constant flow of water of even temperature be secured. Direct connection with the city supply is not practicable, owing to the variations in pressure, and hence in constructing the laboratory building provision was made to install a large tank on the top floor, fed with a supply controlled by a ball-and-cock valve. By this arrangement the level in the tank is maintained constant and the pressure is therefore regular. As the level of the water in the tank is approximately 9 meters above the opening in the calorimeter, there is ample pressure for all purposes. [Illustration: FIG. 14.--Schematic diagram of water circuit for heat-absorbers of calorimeter. A, constant-level tank from which water descends to main pipe supplying heat-absorbers; _a_, valve for controlling supply from tank A; B, section of piping passing into cold brine; _b_, valve controlling water direct from large tank A; _c_, valve controlling amount of water from cooling section B; C, thermometer at mixer; D, electric heater for ingoing water; E, thermometer for ingoing water; _d d d_, heat-absorbers inside calorimeter; F, thermometer indicating temperature of outcoming water; G, can for collecting water from calorimeter; _f_, valve for emptying G.] The water descends from this tank in a large 2-inch pipe to the ceiling of the calorimeter laboratory, where it is subdivided into three 1-inch pipes, so as to provide for a water-supply for three calorimeters used simultaneously, if necessary, and eliminate the influence of a variation in the rate of flow in one calorimeter upon the rate of flow in another. These pipes are brought down the inner wall of the room adjacent to the refrigeration room and part of the water circuit is passed through a brass coil immersed in a cooling-tank in the refrigeration room. By means of a by-pass, water of any degree of temperature from 2° C. to 20° C. may be obtained. The water is then conducted through a pipe beneath the floor to the calorimeter chamber, passed through the absorbers, and is finally measured in the water-meter.