DEVELOPMENT OF HOUSE HEATING 123 



radiation, but it also greatly increases the convection currents 

 which heat the outside edges and corners, and the floor of the 

 room (see Art. 364). 



THE SETTING OF FURNACES 



141. The Furnace. The FURNACE for house heating is 

 little more than a large stove of simple construction inclosed 

 within a sheet-iron jacket or surrounded by brick walls. 

 When the iron jacket is used it is said to have a PORTABLE 

 SETTING; when the brick walls are used it is said to be a BRICK 

 SET FURNACE. In either case, the furnace with its jacket 

 employs the same principles which are employed in the 

 jacketed schoolroom stove, the principal difference being 

 that the furnace is set in the basement or cellar. The air to 

 be heated is led to the bottom of the space inclosed by the 

 jacket by means of sheet-iron pipes running through the base- 

 ment, or better still, by means of large tile or cemented brick 

 passages beneath the basement floor. The heated air is led 

 upward from the top of the jacket to the rooms above, which are 

 to be heated. 



142. Air Supply for the Furnace. The cold air supplied 

 to the furnace is often taken from within the house; a more 

 sanitary method is to supply the furnace with pure, fresh air 

 from without the basement wall. When the second plan is 

 followed, the furnace becomes, not only a heating plant, but also 

 an excellent means of furnishing ventilation as well. By this 

 plan, a considerable stream of fresh air is coming into the house 

 at all times. This is, of course, quite impossible unless some 

 opening is provided to allow an equal amount of air to escape. 

 The ordinary house is often too well built to permit this 

 amount of air to escape through cracks and crevices. The 

 exit may be provided by partly opening a window; it is 

 better, however, to provide fireplaces with flues extending 

 above the roof. Many people do not yet appreciate the great 

 importance of proper ventilation for their homes and there- 

 fore they provide for taking the cold air supply only from within 



