DOMESTIC ECONOMY OF FUEL. 201 



tion of some of the heat which is passing into the chimney to warm 

 the air which feeds the tire. Theoretical considerations show that an 

 advantage of from six to nine per cent, might be obtained from this 

 source, and the experiments which I have made bear out this result. 



But, after we have designed the most effective arrangements for 

 economizing the fuel which warms our dwellings, if that object is to 

 be fully secured, we must arrange to retain the heat in our houses. 

 The architect should devote to these considerations the same care 

 which he now is frequently satisfied with bestowing upon the beauty 

 of the design for a building. The arrangements of the plan should be 

 adapted to the retention of heat. All portions of houses exposed to 

 the air should be formed of materials which are found to be the slow- 

 est conductors of heat. Whatever may have been the mistakes of the 

 manufacturers of fire-grates or kitchen-ranges, the nation has latterly 

 very much disregarded the means of retaining heat in the house. The 

 uniform model house of the speculating builder is constructed with 

 thin walls, thin glass windows, ill-fitting casements, and a roof of slates, 

 with nothing under them. The old half-timbered house was warm, 

 because it had an air space between the inner and outer skin ; the 

 brick-built, stone-faced house is warm because it has, so to say, a double 

 wall. In modern houses it has long been shown that, without much 

 increased expense, the use of walls built hollow will keep the rooms 

 effectually warm and dry, and yet this mode of building is the excep- 

 tion rather than the rule, possibly because it gives the architect or the 

 builder a little additional trouble. A slated roof, if ill-constructed, is 

 a material agent in allowing of the escape of heat, because there is 

 necessarily an inlet for air where the slates overlap. The old thatched- 

 roof, although most dangerous in cases of fire, was a great preserver 

 of heat. In well-built modern houses the slates are laid on felt, which 

 is laid on close boarding, and this arrangement keeps the house warm 

 in winter and cool in summer. As regards the windows, glass ranks 

 high as a non-conductor of heat, and the effect of using thick glass, in- 

 stead of the very thin glass so often seen, is very largely to economize 

 the heat. Evidence of the cooling effect on the air of a room of a win- 

 dow of thin glass is afforded by the cold draught which any one per- 

 ceives when sitting on a cold day near a closed window of thin glass. 

 Proposals have been often made to glaze a window with double panes, 

 and no doubt such a plan is a good means of retaining heat in the room, 

 but the inside of the glass between the panes will in time become dirty, 

 and then it can only be cleansed by removing one of the panes. A 

 more convenient, but more expensive, plan is to adopt the system, 

 which prevails universally in the northern parts of Europe, of a double 

 casement. 



It is not, however, my object here to give a treatise on building. 

 The conclusion which I would draw from these various considerations 

 is, that, if we desire to economize to the utmost the daily expenditure 



