‘HOT WATER. 309 
changes have been made; the cistern has generally been 
abandoned, and boilers of various configurations have been 
adopted. Fig. 29 is a longitudinal section, and the follow- 
Fig. 30, 
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ing is a transverse section of a flued tank boiler, in which 
the surface exposed to the heat being increased, the effect 
required is accelerated, and at the same time a considera- 
ble saving of fuel is effected. 
The conical boiler, invented by John Rogers, Esquire, 
of Sevenoaks, Kent, is formed of two truncated concentric 
ones, with a space of two or three inches between them for 
the water, the furnace being in the inner cone, and the fuel 
supplied from the top. 
Mr Rogers’ boiler was originally surrounded with brick- 
work, but several modifications and improvements of it have 
been introduced ; in some cases it has been fitted up in a 
sheet-iron case, like Arnot’s stove. In the following figure, 
the boiler is placed in a cast-iron stand, with ground circular 
furnace, and register ash-pit doors—a being the furnace, 4 
the boiler, c flow and returning pipes, d the furnace door, e 
smoke-pipe to the vent, f ash-pit, g branders, % hole for 
cleaning the furnace. The best kinds of fuel for this fur- 
nace are coke, gas-cinders, and anthracite; but common 
