HYDRAULIC ENGINES. 67 
of a fire-engine constructed by Bramah, which differs essentially from those 
already described. Upon a strong four-wheeled truck rest the saddles a, cut 
out circularly on top to receive the cylindrical chamber B, made of staves 
or boards and hooped with iron: it is divided into three divisions, A, B, ©. 
A contains the pump-cylinder; the middle portion, B, is the water-box; and 
c receives one of the gudgeons of the centre shaft and the levers or arms 
by which it is worked. 
At a is an opening with a closely-fitting cover, through which the 
interior of the water-chest is cleansed. Above the engine is a box, p, for 
carrying tools, at one end of which, in a separate division, is the air-cham- 
ber £; beneath the engine is a cock, c, to let off the water. At d@ is seen 
the brass pump-cylinder, 10 inches in diameter and 74 inches long for an 
engine to be worked by 10 men. Above this cylinder communicates with 
the air-chamber, and below with the water-chamber through the pipe 7; 
k is a cock which establishes a communication between the pump-cylinder 
and either the water-chamber or with the external air, according as it is 
turned in one direction or the other. When water is to be drawn from a 
well, the cock is turned, as seen in fig. 22, so that the pump-cylinder d is 
opened to the tube on the left, to which is attached a suction-hose reaching 
to the bottom of the well. 
When water is to be drawn from the water-chamber p, the cock & is 
turned in the opposite direction, opening a communication between the 
pump-cylinder and the pipe 7. Beneath the central axle the pump-chamber 
d is divided by a vertical partition, reaching from the axle to the bottom 
of the chamber, and upon each side of the division-wall are valves in the 
bottom of the chamber opening inwards. The axle is packed water-tight 
where it enters the pump cylinder, and also at the joint between it and the 
vertical partition. Attached to the axle within the cylinder are two plates 
or pistons, one upon each side of the partition, which are packed tight by 
rings or disks of leather. In these plates are valves opening upwards. <A 
reciprocating rotary motion is communicated through the brakes o to the 
centre axle, and the plates or pistons attached to it are thus alternately made 
to approach and recede from the stationary partition. The water is thus 
drawn through the valves in the bottom of the cylinder, and forced through 
the valves in the reciprocating pistons into the upper portion of the cylinder 
d, which communicates with the air-chamber £, from which the pipe passes 
which receives the hose. 
Steam-power has also been applied to the working of fire-engines, Braith- 
waite in London being the first who made the attempt. Pl. 14, fig. 24, 
represents a side view of a fire-engine driven by steam; it works on the 
high-pressure principle, and has six horse-power. It has two horizontal 
cylinders, one of which is the steam-cylinder and the other that of the 
forcing-pump ; the pistons of both are on one rod and act at the same time, 
the alternating motion of the steam-piston producing that of the plunger 
immediately. @a@ is a wooden frame which rests on springs that are 
supported on the axles of the wheels; on this wooden frame is an iron one, 
which supports the cylinders and other main parts of the engine; 4 is the 
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