38 



HOT WATER APPARATUS. 



Having devoted considerable time and attention to heating houses with 

 hot water, and watching the thermometer, both out of doors and in the 

 house, for several years, but more particularly during the last and present 

 year, and by accurate calculations of the number of feet of surface glass 

 exposed to the weather," Mr. Thompson adds, " I am enabled to estimate 

 very correctly the number of feet of surface of pipe required to command, 

 with all extremes of weather, any specified degree of heat, either in the 

 stove or greenhouse : the want of proper attention to this highly important 

 part, namely, calculating the radiating surface of glass, and then esti- 

 mating the proper quantity of pipe necessary to produce certain degrees 

 of heat in all weathers, is the cause of many of the complaints against the 

 system of heating by means of hot water.'' 



FURNACES ADAPTED FOR HOT WATER BOILERS. 



As a much more moderate and uniform heat is required for the proper 

 working of a hot water boiler, than for many other purposes — the steam 

 engine for example — a furnace, so constructed that a moderate heat 

 may be obtained, and by which combustion may go on slowly, is all that 

 is required. 



The following excellent directions on this subject, by Mr. Hood, are 

 worth attention. " The heat should be confined, as much as possible, 

 v^ithin the furnace, by contracting the farther end of it, at the part 

 called the throat, so as to allow only a small space for the smoke 

 and inflamed gases to pass out. The only entrance fos the air should 

 be through the bars of the grate, and the heated gaseous matter will 

 then pass directly upward to the bottom of the boiler, which will act 

 as a reverberatory, and cause a more perfect combustion of the fuel 

 than would otherwise take place. The hghtness of the heated gaseous 

 matter causes it to ascend the flue, forcing its passage through the throat 

 of the furnace with a velocity proportional to the smallness of the pas- 

 sage, the verticle height of the chimney, and the levity of the gases arising 

 frcHii their expansion by the heat of the furnace." 



" In this arrangement the whole of the air which supports the com- 

 bustion passes through the fire below, and any air admitted at the furnace 

 door, between the fuel and the boiler, reduces the intensity of the heat." 

 We ought here to observe that the most extravagant waste of fuel arises 

 from air being admitted in this manner, either from improper fm-nace doors 

 or from their being left open, or partially so, all cases of the most common 



