Sectional drawing (scale 1:4) of Messenger's patent 1867, high pressure vertical water-tube boilers, one with "heat pegs" and one without them, framed and glazed in Museum
In this arrangement of boiler, patented in 1867 by Mr. T. Messenger, a certain amount of tube surface is introduced. From the inner sides of the firebox project curved tubes reaching to the top, while in the central space is a baffle block to deflect the flame amongst them. A curtain of sheet iron is placed in the water space to increase the circulation, while heat pegs or studs projecting into the flame space are added, and these are stated to have a heating surface of equal value to that of the sides of the box.
