FURNACE AND ITS APPENDAGES. 



flues. The flame and heated air proceeding from the burning fuel 

 arising from the grate, and rushing towards the back of the fur- 

 nace, passes over the fire-bridge E, and is carried through the 

 flue P which passes under the boiler. This flue (the cross section 

 of which is shown in fig. 9, by the dark shade put under the 

 boiler), is very nearly equal in width to the bottom of the boiler, 

 the space at the bottom of the boiler, near the corners, being only 

 what is sufficient to give the weight of the boiler support on the 



Fig. 8. 



masonry forming the sides of the flue. The bottom of the boiler 

 being concave, the flame and heated air as they pass along the 

 flue rise to the upper part by the effects of their high temperature, 

 and lick the bottom of the boiler from the fire-bridge at E to the 

 further end G. 



At G the flue rises to H, and turning to the side of the boiler at 

 1 1, conducts the flame in contact with the side from the back to 

 the front ; it then passes through the flue K across the front, and 

 returns to the back by the other side flue L. The side flue is 

 represented, stripped of the masonry, in fig. 7, and also appears in 



13 



