HEATING. 63 



full service out of such a boiler it will be necessary 

 to carry a hot fire, and as a result a large per cent 

 of the heat goes up the chimney. Boilers, there- 

 fore, should be selected with due regard to (i) the 

 amount of direct heating surface, (2) perpendic- 

 ular circulation of the water in the boiler, (3) the 

 capacity for fuel, and (4) conveniences in the mat- 

 ter of suitable grates, drafts, and doors. Most 

 boilers are rated on the number of square feet of 

 pipe they will heat. Asa rule, at least twenty- 

 five per cent margin should be allowed on these 

 figures in order to be on the safe side. For 

 example, if a boiler is rated to heat one thousand 

 square feet of pipe it should not have more than 

 seven hundred or seven hundred and fifty feet 

 put upon it. It may heat the thousand feet 

 at a pinch, but the grower wants it to 

 heat the pipe at all times with a slow 

 fire that will stand without attention 

 at least six or seven hours. 



The saddle, conical, and locomotive types of 

 boilers are probably as efficient as any we now 

 have, and by taking any one of these and fitting 

 it up with the modern improvements in the way 

 of deep fire box, grates, ash-pit, door and flue 

 drafts, and dampers, it would, in all probability, 

 do the work more economically and efficiently 

 than a large number of the intricate forms now on 

 the market. There is the keenest competition 

 among boiler makers, and as a rule, they are to be 



