(under subclass 51) Devices having two diameters, the small diameter being over the firebox and the large diameter being beyond the bridge wall. The offset portion of the large diameter is provided with longitudinally extending fire tubes, through which the products of combustion from the firebox pass and then are passed through return fire tubes extending the whole length of the boiler. The products of combustion may then pass to the outlet flue at the front end of the boiler, or they may pass rearwardly above the boiler to the outlet flue located at the rear end, and in their final rearward passage may pass through fire tubes in an upwardly offset portion of the boiler.
SEE OR SEARCH THIS CLASS, SUBCLASS:
56, 81, 86, 110, and 191, for analogous structure.
