In another form of arrangement, having the same end in view by means of heated air, the air, instead of passing through an enclosed space between the outer case and the inner stove, passes over a surface of metal which is heated either by a fire underneath, or, which is better, by steam or hot water contained in pipes. The temporary House of Commons, the Reform Club-house, and many other buildings, are warmed in this way. The following simple and cheap form of stove has been erected in the cottages of Sir Stewart Monteath’s labourers. The accompanying figure represents a section of the stove, the principle of which will be understood from the following explanatory notes:-- [Illustration 1. _Kitchen fire._ 2. _Chimney._ 3. _Hot air Chamber._ This is a cast-iron box, which forms the back of the kitchen grate. 4. _Cold air pipe, or passage_; made with brick, or stone, or iron piping, communicating with the open air for the purpose of feeding the hot air chamber with an ascending current of fresh air. 5. _Hot air pipe_, receives the ascending current of air, which becomes heated by passing over the back of the fire. At the top this pipe branches off at right angles, and terminates near the floor in the two sleeping rooms above. 6. _Gratings_ to admit the warm air from the hot-air pipe into the bed-rooms. The addition of sliding valves over the face of the gratings would serve to cut off the current of warm air during the summer, and when not otherwise required. 7. _Sitting-room_, into which sufficient heat is radiated from the hot air chamber, not only to warm the apartment, but even to dry wet linen.] By means of one common fire in a stove of the above description, a four-roomed cottage can be comfortably warmed, and kept dry throughout. Warming Buildings by Steam.