HEATING BY HOT WATER. 181 
greatest importance, often making all the difference 
between economy and extravagance in fuel—between 
efficient and non-efficient working. This ought con- 
sequently never to be left to ignorant or inexperienced 
persons. The best method of setting most of the forms 
of saddle boilers is shown in Fig. 120. Flues situated 
on the top or crown of a boiler are comparatively ineffectual 
and useless, as heat strikes downwards to a very limited 
degree only; such should therefore be avoided as far 
as possible, or if employed at all, only to carry the nearly 
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Fig. 120. 
spent fumes, etc., back to the chimney the last time. 
In all cases the endeavour should be to keep the current 
of heated air, or escape, as /ow down as possible, after 
leaving the fire ; in fact, if a decided dip can be arranged 
at some point between the fire and the chimney there 
will be a considerable gain in heating power and general 
efficiency. This may usually be effected by fixing a 
vertical ‘‘mid-feather,"’ or diaphragm in each of the side- 
flues, about half-way between the front and back of the 
