ON THE SETTING OF STEAM BOILERS. 135 



the shortest cut to the chimney, it is necessary, in this case, 

 to unite the side flues into one, in order that both may he 

 utilized. If there is not length for this, it is better to take 

 the draught the other way, namely, split it at the back and 

 return it under the bottom, by which arrangement the 

 side flues will pull equally. 



But whichever way it is done, the splitting of the draught 

 at all is an objection, as I shall show later on. Another 

 objection to this form of setting is, that tlie boiler rests on 

 two brick walls. A certain portion of the surface is thus 

 rendered useless, and this in the best position, while any 

 leakage from the top, or damp from the ground, may be 

 caught by these walls, and unseen corrosion may go on. 



But the chief objection lies in the smallness of area in 

 the flues. It is impossible to get a good draught, and there- 

 fore good coudjustlon, when the flues are small. The gases 

 are so retarded by friction and want of space for expansion, 

 that the entrance of air into the furnace is chocked and the 

 fire burns dead. To remedy this, a huge chimney has to be 

 huilt, much higher than is at all necessary, in order to pull 

 the gases through; the result of which is, they have not 

 time to part with their heat in their passage through tlie 

 flues, and a largo portion of it escapes up the chimney. In 

 addition to this, a largo deposit of soot always takes place m 

 these small flues, which coats the surface of the boiler and 

 still further reduces the area and impedes the draught. 

 Inspection is rendered difficult, as some of us, who have had 

 to worm and screw ourselves through the flues of a small or 

 medium sized boiler, know by sad experience ; and it will no 

 doubt be admitted that in such cases the inspection is only 

 half done, and the boiler is worked at great risk. 



Referring now to the other form of setting, viz., the 

 wheel draught. I do not find these objections existing, at 



