Fig. 3269.

The efficiency of the heating surface in this class of boiler is increased from the fact that, as the heat does not pass direct through the boiler, it impinges against the surface. In [Fig. 3269], for example, the exit from the spherical fire box is on one side of the boiler, and the uptake on the other, the heat passing from the fire box into a combustion chamber, and thence through the horizontal fire tubes to the uptake.

Fig. 3270.

The crown sheet is here stayed by gusset stays, but if made spherical, as in [Fig. 3270], the stays may be omitted.

VOL. II.BOILER FOR STATIONARY ENGINES.PLATE XXVIII.
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Fig. 3271.