escape through any cracks or openings in the stove into the room. Prof. Chandler, having kept a record of accidents from this cause, had accumulated a formidable list of suffocations due to the use of the damper. The danger was now somewhat lessened by providing dampers with perforations in the center, which allowed the gases to escape when the damper was closed. As regards the maintenance of pure air in houses, the preference was given to the open fire-place. The hot-air furnace deriving a supply of pure air from out of doors was, when properly constructed, a very satisfactory method of heating, but in city houses the mistake was often made of carrying the cold air duct of the furnace to the front of the house, where it was exposed to the dust of the streets. It should be taken from the rear end of the house, and carried some distance above the surface of the yard. It was an excellent expedient to insert in the cold air duct a wire screen to hold a layer of cotton to retain the floating impurities which might enter the air-box. This could be removed from time to time, and the cotton replaced. Steam heating has been objected to by many for reasons in no wise due to the apparatus, but to neglect in the use of it. The complaint of closeness where steam is used is due to the fact that a room containing a steam radiator can be heated with every door and window closed, and no fresh air admitted, while with stoves and open fire-places a certain quantity of fresh air must be admitted to maintain the fire. Where radiators are used, the ventilation of the rooms should, therefore, be looked after. Again, the complaint that steam apparatus has an unpleasant odor is due to the fact that the radiators are allowed to become covered with dust, which is cooked, and gives rise to the smells complained of. The radiator should be from time to time cleaned. When these precautions are taken, no means of heating is more satisfactory than steam. Sewer gas is another source of contamination; this is a very indefinite term, to which formerly many false and exaggerated properties of causing specific diseases were attributed. It is now, however, recognized to mean simply the air of sewers, generally not differing very greatly from common air, containing a certain proportion of marsh gas, carbonic acid, and sulphureted hydrogen, etc. No one of these gases, however, is capable of producing the diseases attributed to sewer gas. Careful research has shown that it is the sewage itself, containing germs of specific disease, which is added to the air in the sewer by the breaking of bubbles of gas on its surface, which is the cause of the diseases associated with sewers.