There is no department of science, as applied to practical matters, which has so often baffled experimenters as the healthful mode of warming and ventilating houses. The British nation spent over a million on the House of Parliament for this end, and failed. Our own Government has spent half a million on the Capitol, with worse failure; and now it is proposed to spend a million more. The reason is, that the old open fire-place has been supplanted by less expensive modes of heating, destructive to health; and science has but just begun experiments to secure a remedy for the evil. The open fire warms the person, the walls, the floors, and the furniture by radiation, and these, together with the fire, warm the air by convection; for the air resting on the heated surfaces is warmed by convection, rises and gives place to cooler particles, causing a constant heating of its particles by movement. Thus, in a room with an open fire, the person is warmed in part by radiation from the fire and the surrounding walls and furniture, and in part by the warm air surrounding the body. In regard to the warmth of air, the thermometer is not an exact index of its temperature. For all bodies are constantly radiating their heat to cooler adjacent surfaces until all come to the same temperature. This being so, the thermometer is radiating its heat to walls and surrounding objects, in addition to what is subtracted by the air that surrounds it, and thus the air is really several degrees warmer than the thermometer indicates. A room at 70° by the thermometer is usually filled with air five or more degrees warmer than this. Now, the cold air is denser than warm, and therefore contains more oxygen. Consequently, the cooler the air inspired, the larger the supply of oxygen and of the vitality and vigor which it imparts. Thus, the great problem for economy of health is to warm the person as much as possible by radiated heat, and supply the lungs with cool air. For when we breathe air at from 16° to 20°, we take double the amount of oxygen that we do when we inhale it at 80° to 90°, and consequently can do a far greater amount of muscle and brain work. Warming by an open fire is nearest to the natural mode of the Creator, who heats the earth and its furniture by the great central fire of heaven, and sends cool breezes for our lungs. But open fires involve great destruction of fuel and expenditure of money, and in consequence economic methods have been introduced, to the great destruction of health and life.