This section is from the book "Commercial Gardening Vol1", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The "saddle " boiler is still very popular amongst all classes of growers, especially amongst the "smaller" men who cannot at first, perhaps, afford to instal the dearer kinds. The plain "saddle" boiler, which has an opening right through, still does serviceable work, but whenever possible it is replaced by the type having a check or waterway end (fig. 173). There are many types of these saddle boilers on the market, one of the flued type being shown in figs. 174, 175, in elevation and section. It is known as the Gold Medal boiler, and is made of wrought iron. The heat from the fire (b) strikes the waterway end (e) before ascending into the centre flue (c), whence it is deflected into the flues right and left (d), and then goes over the top of the boiler. In the figures the ashpit is shown at a, the flow pipe at h, the return pipes at i, the sliding doors for cleaning out the flues at /, and the draw-off cocks at g. These are useful when it is intended to clear the water out of the boiler. At l the hollow space is shown round the boiler to utilize the heat given off from the surface.