Fig. 29 illustrates Boyle’s arrangement for cooling the air entering a room in hot weather. It consists of an air-inlet tube of bracket form, made of iron. The part which penetrates the hole in the wall has an outer casing, so that a space of about ½ in. is left between, which is packed with a non-conducting substance, for the purpose of preventing the heat from the wall penetrating into the interior of the opening and acting upon the blocks of ice, which are placed in a movable drawer, and kept in position by means of open galvanised iron or copper-wire netting. The front of the drawer is also double, and packed same as casing. The outer air entering through the grating is deflected by a metal shield on to the suspended blocks of ice, and from thence on to the ice at the bottom of the drawer, and thence up the tube into the room. The air is not only cooled, but purified thoroughly from dust. See also p. 991. =Warming.=--In connection with warming an apartment, it is obviously a necessary condition that the warmth shall be conserved as much as possible. Hence there is an evil in having too much glass, as it cools the room too fast in the winter season: 1 sq. ft. of window glass will cool 1½ cub. ft. of warm air in the room to the external temperature per second; that is, if the room be warmed to 60° F., and the thermometer stands at 30° F. outside, there will be a loss of 90 cub. ft. of warm air at 60° per second from a window containing a surface of glass of 60 sq. ft. In colder climates than that of England, this subject is of much greater importance. In America, for instance, during the cold weather, there will always be found, no matter how tightly or closely the sashes are fitted and protected with weather-strips, a draught of cold air falling downward. This arises from the contact of the heated air with the cold glass, which renders the air cooler and heavier, and causes it to fall. The air, at the same time, parts with a considerable proportion of its moisture by condensation upon the glass. The cold air thus formed falls to the floor, forming a layer of cold air, which surrounds the feet and legs, while the upper part of the body is enveloped in overheated air. The layers of cold and warm air in an apartment will not mix. The warm air will not descend, and the cold air cannot go upward, except the one is deprived of its heat by radiation, and the other receives its heat by actual contact with a heated surface. This radical difference in the upper and lower strata of atmosphere of the rooms, in which people live during the cold season, is the prolific cause of most of the throat and lung diseases with which they are afflicted. Double windows to the houses, therefore, would not only be a great economy as to fuel, but highly conductive to human longevity.