The calorimeter 10 Fundamental principles of the apparatus 10 The calorimeter chamber 11 General construction 14 Prevention of radiation 17 The thermo-electric elements 19 Interior of the calorimeter 20 Heat-absorbing circuit 22 Thermometers 26 Mercurial thermometers 26 Electric-resistance thermometers 28 Air-thermometers 28 Wall thermometers 29 Electrical rectal thermometer 29 Electric-resistance thermometers for the water-current 29 Observer's table 31 Connections to thermal-junction systems 33 Rheostat for heating 34 Wheatstone bridges 34 Galvanometer 35 Resistance for heating coils 35 Temperature recorder 36 Fundamental principle of the apparatus 38 The galvanometer 39 The creeper 40 The clock 42 Installation of the apparatus 42 Temperature control of the ingoing air 43 The heat of vaporization of water 44 The bed calorimeter 45 Measurements of body-temperature 48 Control experiments with the calorimeter 50 Determination of the hydrothermal equivalent of the calorimeter 52