In the improved Cornish or Trentham boiler, shown at fig. 176, we have a circular or cylindrical type, being a modification of the Cornish steam boiler. The boiler consists of wrought-iron cylinders welded together, and is seated on two iron chairs or supports as shown at a a. The front chair forms the frame for the lower and upper flue doors, shown at b b, by means of which the soot can be easily removed. At the bottom of the cylinder is a plug. c, which, when unscrewed, allows the water and all accumulation of dirt in the boiler to escape when necessary. The two furnace doors are shown, one open, at d, while e is the flow pipe on top, near the back, and / the return pipe low down at the side towards the front. In the Cornish or Trentham boiler a large water space is exposed to the fire, and as the heat has most force on the upper side, where there is less likelihood of matter accumulating, there is an excellent circulation of hot water through the flow into the pipes in the houses.

Saddle  Boiler with Waterway End.

Fig. 173. - " Saddle " Boiler with Waterway End.

Gold Medal Boiler (elevation).

Fig. 174. - Gold Medal Boiler (elevation).

Gold Medal Boiler (longitudinal section).

Fig. 175. - Gold Medal Boiler (longitudinal section).