1S71.] 
cannell’s boiler. 
87 
It consists of nine or more separate castings, placed one upon the other, the whole resting 
upon brickwork, which forms the ashpit. The base, or No. 1 casting, consists of a hollow 
rectangular frame, into which are fixed eight (more or less, according to size) circular hollow 
fire-bars. The return pipes enter near the back of this casting, and the flow-pipe issues near 
the front, while in front is a discharge-pipe for cleansing the interior. The ashpit is enclosed 
by a door hung on a cast-iron frame in the usual way, and the furnace door is similarly hung. 
Upon casting No. 1 are placed four other separate hollow castings; Nos. 2 and 3, forming 
the sides of the furnace, are fluted and placed parallel with the hollow fire-bars, and are of 
such a length that the two remaining castings, Nos. 4 and 5, which form respectively the back 
and front of the apparatus, may be flush with the ends of the first casting. No. 4 is large 
enough to cover the whole end of the apparatus, and is connected by pipes at the bottom with 
Nos. 2 and 3 respectively, and at the top on each side with casting No. 11. No. 5 is of such a 
height as to be level with the top of No. 6. The front above this is to be built up in 
brickwork, with three sliding soot doors to allow the flues to be properly cleaned out. No. 5 
Cannell’s Registered Boiler. 
is connected at the bottom with Nos. 2 and 3, and at the top on each side with No. 6—a hollow 
fluted casting which forms the crown of the furnace, having a space left at the back, opening 
upwards, to allow the fire to pass out of the furnace under a separate and hollow casting 
(No. 7), which, when fixed, forms two flues communicating, by means of other flues formed by 
similar castings, with a rectangular opening at the top for regulating the draught, and for the 
passage of the smoke into the chimney. 
The circulation of the water from and into each separate casting is effected by means of 
four sets of pipes affixed externally to the castings, two sets being placed on each side of the 
apparatus. If desired, the crown or top casting with the flow-pipe can be placod upon Nos. 
2 and 3, and worked without the flues until required. The heat from the fire passes 
between castings Nos. 2 and 3 until it arrives at the opening left at the back of No. 6, where 
it divides, and passes upwards towards the front through the two flues formed by casting 
No. 7; it then returns towards the back through the two flues formed by casting No. 8, 
again passing and repassing along Nos. 9 and 10, and thence travelling through No. 11 to the 
chimney. Thus the hot air is made to pass six times through the internal length of the 
apparatus before escaping. 
In this new boiler, the parts, being all in square sections, can be cast of an 
equal and regular substance, thus avoiding one fertile source of fracturo and 
