(under subclass 345) Devices having vertical water tubes beyond the bridge wall and above the firebox, with any type of drums or headers communicating with the tubes and so arranged that the products of combustion pass over the bridge wall and upwardly through a separate passage to the front of the boiler before they are discharged.
SEE OR SEARCH THIS CLASS, SUBCLASS:
350, for similar art where there are boilers with vertical tubes wholly over the firebox and having the products of combustion pass out at one end of the firebox and return through the vertical tubes above the firebox.
