he rate at which it is delivered, must
depend on the means possessed of making use of the water.

The average size of fire-engines may be taken at two cylinders of 7
inches diameter, with a length of stroke of 8 inches, making forty
strokes each per minute. This sized engine will throw 141 tons of
water in six hours, and allowing one-fourth for waste, 176 tons would
be a fair provision in the tanks for six hours' work; this quantity
multiplied by the number of engines within reach, will give an idea of
what is likely to be required at a large fire. If, however, there are
steam-engines to keep up the supply through the mains, the quantity of
water kept in readiness may be reduced to two hours' consumption, as
it is likely that the steam-engines would be at work before that
quantity was exhausted. This is what may be supposed to be required,
in cases of serious fires in dockyards, in large stacks of warehouses,
or in large manufactories.

[Illustration: FIG 6. Opening for Suction-pipe.]

Where water can be had at nearly the level of the premises, such as
from rivers, canals, &c., if it is not thought prudent to erect
elevated tanks, the water may be conducted under the surface by large
cast-iron pipes, with openings at such distances as may seem advisable
for introducing the suction-pipes (Fig. 6). This plan should not be
adopted where the level of the water is more than 12 feet below the
surface of the ground, as although a fire-engine will, if perfectly
tight, draw from a much greater depth than 14 feet (2 feet being
allowed for the height of the engine), still a very trifling leakage
will render it useless for the time, at such a depth.

The worst mode of supplying engines with water is by covered sunk
tanks; they are generally too small, and unless very numerous, confine
the engines to one or two particular spots, obliging the firemen to
increase the length of the hose which materially diminishes the effect
of the fire-engine. If the tank is supplied by mains from a reservoir,
it would be much better to save the expense of the tank, and to place
plugs or firecocks on the water-pipe. Another evil in sunk tanks is,
that the firemen can seldom guess what quantity of water they may
depend upon, and they may thus be induced to attempt to stop a fire,
at a point they would not have thought of if they had known correctly
the quantity of water in store.

Where sunk tanks are already constructed, they may be rendered more