HYDRAULIC ENGINES. 65 
the preference over conical valves, as they close perfectly, even when coming 
down a little inclined, which is not the case with the latter. Plane or hinge- 
valves consist of square or round plates of brass, well polished, and moving 
on hinges ; or else a disk of leather is serewed between two plates of metal, 
one of which is a little smaller, the other a little larger than the opening to 
be closed, the leather disk thus closing the opening, while a prolongation of 
it serves as a hinge. ‘The valves in the pipe connecting the cylinders and 
air-chamber are always hinge-valves in an oblique position. 
We will now proceed to explain the construction of different kinds of 
fire-engines, with the aid of plate 14. J/g. 1 is an elevation, fig. 2 a section 
of the simplest machine of the kind, which is readily worked and carried 
about by one person, and, having no air-chamber, throws an intermittent 
stream. a is the cylinder, 8 the suction-valve, c the perforated suction-pipe ; 
when the plunger, 1, is raised, the water enters the cylinder through zn, and 
in descending the plunger drives the water through the pipe, p, and the 
valve, F, into the hose, a, and expels it in a stream oe the nozzle, Hu. The 
crutch, L, serves to manage and support the machine. 
A foeable fire-engine with a single cylinder, which acts far more power- 
fully than the shige: but Late several persons for its management, is 
represented in jigs. 3 and 4, the former being a cross-section in front of the 
air-chamber, the latter a longitudinal section. In the trough, a, is the sill, 2, 
to which the main parts of the engine are screwed; ¢ is the plunger, @ the 
air-chamber, with the orifice, 7, opening into the branch-pipe, 2 #, which is 
movable in every direction by means of the joints at g, 4, and ¢, and the 
construction of which is shown in detail in jig. 18. The pump is worked 
by the lever, x; the levers, p p, which turn about the bolts, ¢ g, serve for 
transporting the engine, when they bear against the projections, 7 7. 
A double-acting portable fire-engine of very simple construction is that 
by Letestu, having pistons and valves on the principle explained above 
in speaking of his pump. /7g. 11 is a longitudinal section, fig. 12 a top 
view, jig. 13 a cross-section through the air-chamber, fig. 14 a horizontal 
section along the lower dotted line in jig. 11, and jig. 15 a front view of the 
engine. On a strong support, 4B, provided with the rings, o, through 
which poles may be passed for transportation, rests the trough or water-box, 
D; in its centre is the air-chamber, &. ‘The piston, x, in ascending admits 
water into the cylinders, u, and in descending forces it through the valve, a, 
into the air-chamber, whence it is expelled through the pipe, o, to which the 
hose and branch-pipe are screwed. At u the piston-rods are attached to 
the lever or balance-beam, m, which moves about the centre-bolt, p, and is 
worked by means of the arms, Nn N. 
A more complex fire-engine is that by Pontifex, of London, which is fre- 
quently used on board ships, on account of its requiring but little space. 
Fig. 5 represents a longitudinal and jig. 6 a cross-section. It is inclosed in 
a box, A, which has at the bottom the projecting leaves, ¢ (the one on the 
left hand is omitted), that fold up about a hinge, f; when the engine is in 
use they are turned down and a part of the men stand on them, giving 
stability to the engine. The upper part of the box consists of two pieces 
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