Evening star. [volume] (Washington, D.C.) 1854-1972, 1906-10-06

to go ahead. slow down or stop. He thus
saves the time and labor of the switch
tender, who otherwise must run from one
switch to another.
You have often noticed how the modern
railway line Is punctuated by uprights
from which jut out blade-like panels set
at different angles to operate the trains.
These ''semaphores'' are usually arranged
in pairs, one above the other. and on roads
using the telegraph block or manual"
system the upper arm or home signal
gives the indications for the next block
ahead-the distance between the next two
signal, now generally nicked or fish
tailed in the end, gives the indications
for the second block ahead. When either
arm Is dropped the track is clear, and
in the corresponding block. Thus II the
upper arm is down and the lower horizontal
there Is no train in the first but there is
one in the second. block ahead A casting
glass spectacle" which drops over the
normally white light Of the signal post
when the arm Is raised to stop" When
the arm drops the white light shines out
to give the ALI, clear" signal, which on
some roads is also given by a green spec
tacle' covering the light while the arm is
hanging Where there are two parallel
tracks the semaphores are usually set in
two pairs on double bracket supported
by one post. each pair of arms giving the
home and distant signals for Its side
of the track. But where more than two
tracks run side by side the arms are usu-
ally arranged on a bridge spanning the
rails, each superimposed pair being placed
directly above the track which 1t opera tes
In the signal towers of the manual sys-
tenn the levers are connected with the sig
nails and switches by long stretches of
jointed gas pipe moved upon rollers within
the long boxes which you have often seen
lining the track. In large railway ter
minal using this system five or more men
are needed to manually force these levers
into position.
clock and Block" System.
In conjunction with this manual system
with It's scattered towers connected by
telegraph, some railways now use the con
trolled manual or flock and block" sys-
tenn. In this an electric controlling ap-
paratus signals a train into the next block
section only when the consent Of the tower
man at both the entering and outgoing ends
Is concurrently given. Thus the near tower
cannot give the "all clear" signal until the
next tower beyond, after noting that the
train ahead has passed him, electrically re-
leases the gearing.
Automatic Block System.
But the most nearly perfect means of train
control is afforded by the automatic block"
system. In this the switches and signals
are operated by electric currents flowing
through the rails OF the DOCK sectlon TO pe
protected. From a battery at the outgoing
end of a block section the current flows
through the right-hand rail to the signal
at the entering end, thence across the track
through a coil connected with the latter
signals and back through the left-hand
rail to the battery whence it started When
the track is free the coil receives the cur
rent and by means Of a magnet or other
continuance which it controls holds the
rear signal in an "all clear position
Now, If there is train in the section It's
metallic wheels and aXles make from ran