_Insulation of water-pipes through the wall._--To insulate the water-pipes as they pass through the metal walls of the calorimeter and to prevent any cooling effect not measured by the thermometers presented great difficulties. The device employed in the Middletown chamber was relatively simple, but very inaccessible and a source of more or less trouble, namely, a large-sized glass tube embedded in a large round wooden plug with the annular space between the glass and wood filled with wax. An attempt was made in the new calorimeters to secure air insulation by using a large-sized glass tube, some 15 millimeters internal diameter, and passing it through a large rubber stopper, fitting into a brass ferule soldered between the zinc and copper walls. (See N, fig. 25.) So far as insulation was concerned, this arrangement was very satisfactory, but unfortunately the glass tubes break readily and difficulty was constantly experienced. An attempt was next made to substitute hard-rubber tubing for the glass tube, but this did not prove to be an efficient insulator. More recently we have used with perfect success a special form of vacuum-jacketed glass tube, which gives the most satisfactory insulation. However, this system of insulation is impracticable when electric-resistance thermometers are used for recording the water-temperature differences and can be used only when mercurial thermometers exclusively are employed. The electric-resistance thermometers are constructed in such a way, however, as to make negligible any inequalities in the passage of heat through the hard-rubber casing. This will be seen in the discussion of these thermometers. _Measuring the water._--As the water leaves the respiration chamber it passes through a valve which allows it to be deflected either into the drain during the preliminary period, or into a small can where the measurements of the rate of flow can readily be made, or into a large tank (G, fig. 14) where the water is weighed. The measurement of the water is made by weight rather than by volume, as it has been found that the weighing may be carried out with great accuracy. The tank, a galvanized-iron ash-can, is provided with a conical top, through an opening in which a funnel is placed. The diagram shows the water leaving the calorimeter and entering the meter through this funnel, but in practice it is adjusted to enter through an opening on the side of the meter. After the valve _f_ is tightly closed the empty can is weighed.