EXPLANATION OF THE PLATES. 
405 
REFERENCES TO THE DRAWING, PLATE LXXXIV. 
A, Cylinder. 
B B B, Nozles and valves. 
C C, Condensing cistern. 
D, Air pump. 
E, Eduction pipe to condenser. 
F, Expansion tappet. 
G, Damper barrel for regulating the 
valves. 
H, Main beam. 
I, Sliding counter weight. 
K, Hoisting beams. 
L L, Cranes for raising cylinder and 
pump covers. 
M M, Catch pins. 
N, Cold water pump. 
0 0, Hot water pump and air vessel. 
P, Pump rod. 
Q Q, Well. 
R, Working barrel of main pump.. 
S S, Clack barrels. 
T, Air vessel. 
V, Main pipe. 
This engine is single acting, the diameter of the cylinder is sixty-five inches, 
and the length of stroke eight feet; the diameter of the working barrel of the 
main pump is twenty-five inches, and the length of the stroke also eight feet. 
The boilers are six feet wide, eight feet high, and twenty-five feet long. 
The operation of this engine and its appurtenances being nearly similar to the 
action of other engines before described, it is scarcely necessary to advert to it but 
for the purpose of explaining that its effective action is only in one direction, viz., 
during the descent of the cylinder piston. It may be explained as follows:—the 
progress of blowing through # being accomplished, the three valves j- shut again, 
and the injection cock opened, the steam and eduction valves are opened, the 
former to admit the steam from the boiler into the top of the cylinder, and the 
latter to permit its egress from the bottom of the cylinder to the condenser. The 
equilibrium valve remaining shut, the pressure of the steam acting above the 
piston, with the vacuum underneath it, is sufficient to move the piston, and as it 
approaches the end of the stroke, or bottom of the cylinder, the hand gear tappets, 
and catches operate, first, to shut the steam valve, secondly the eduction valve, and 
lastly, when at the bottom of the stroke, to open the equilibrium, and thus open 
the communication between the top and bottom of the cylinder, the counterbalance at 
the outer or pump end of the beam then exerts a force sufficient to move the 
* Opening the valves for the steam to pass from the boiler into the cylinder and through the nozles 
to the condenser, and thus expel the air, vapour and water through the blow valve and valves of the 
air pump. 
f Nozles in front of cylinder; upper steam-valve ; centre equilibrium valve ; lower eduction 
valve.