54 
THE TELEGRAPH 
We shall now describe the peculiar valves that are used for 
despatching and receiving the carriers. 
Earley's Valves .—These valves are represented in Figs. 19, 
20, and 21, and they act in the following manner :—• 
When a carrier has to be received from the communicating 
office, the stud b, Fig. 21, is pressed : a valve in the box v, is 
thus opened and the vacuum vessel is thus connected with the 
cylinders c and D, through the pipe h and j • by the effect of 
atmospheric pressure, the piston of the cylinder is lowered and 
completely closes the cover of 
the box e. This cover is 
formed of a plate of glass 
mounted in a copper frame 
provided with india-rubber 
round its edges. At the same 
time, the piston of the cylinder 
d is raised and kept up at its 
highest position by the stop 
a on its rod, which rests on 
the projection of the piece t, 
oscillating about its upper 
end, and it is pressed by a 
steel spring against the piston- 
rod. The movement of this 
rod opens a valve that puts 
the cylinder H in communica¬ 
tion with the vacuum reser¬ 
voir. The air in the box e 
is thereupon rarefied, and so is that in the underground tube 
which is connected with the box e by the pipes. The carrier, 
which has previously been placed in the extremity of this 
pipe, is then drawn towards the box e, and on its entry therein, 
severs the communication with the vacuum reservoir in the 
manner following :— 
By striking against the india-rubber disc r, shown by 
dotted lines, it opens, by its impetus, a valve by which e and I 
are put into communication ; exhaustion then takes place in 
the box i and in the cylinder k, which are connected by the 
pipe g ; the piston of this cylinder is pushed back, and its rod, 
acting on the hinged lever p 9 causes the rod q to slide and 
Fig. 19. 
