The interior of the chamber and all appliances are constructed of metal except the chair in which the subject sits. This is of hard wood, well shellacked, and consequently non-porous. With this calorimeter it is desired to make studies regarding the moisture elimination, and consequently it is necessary to avoid the use of all material of a hygroscopic nature. Although the chair can be weighed from time to time with great accuracy and its changes in weight obtained, it is obviously impossible, in any type of experiment thus far made, to differentiate between the water vaporized from the lungs and skin of the man and that from his clothes. Subsequent experiments with a metal chair, with minimum clothing, with cloth of different textures, without clothing, with an oiled skin, and various other modifications affecting the vaporization of water from the body of the man will doubtless throw more definite light upon the question of the water elimination through the skin. At present, however, we resort to the use of a wooden chair, relying upon its changes in weight as noted by the balance to aid us in apportioning the water vaporized between the man and his clothing and the chair. The walls of the chamber are semi-rigid. Owing to the calorimetric features of this apparatus, it is impracticable to use heavy boiler-plate or heavy metal walls, as the sluggishness of the changes in temperature, the mass of metal, and its relatively large hydrothermal equivalent would interfere seriously with the sensitiveness of the apparatus as a calorimeter. Hence we use copper walls, with a fair degree of rigidity, attached to a substantial structural-steel support; and for all practical purposes the apparatus can be considered as of constant volume. Particularly is this the case when it is considered that the pressure inside of the chamber during an experiment never varies from the atmospheric pressure by more than a few millimeters of water. It is possible, therefore, from the measurements of this chamber, to compute with considerable accuracy the absolute volume. The apparent volume has been calculated to be 1,347 liters. OPENINGS IN THE CHAMBER.