TEAIN- SIGNALLING IN THEORY AND PRACTICE. 
283 
jive times^ it indicates that the line is blocked, and that nothing 
must be allowed to come on until a signal has been given that the 
line is clear again^ which latter signal consists of three blows 
givenand taken twice. The telegraphinspectors give sign of their 
presence and test the condition of the apparatus by exchanging 
six blows; and an erroneous signal is cancelled by se-ue?! blows. 
The simplest case of deviation from a general code of 
signals is when the trains of two companies travel on the same 
lines^ as the South-Eastern and the Brighton trains between 
London and Bed-hill. In this case one blow indicates a South- 
Eastern train^ whether up or down ; and two blows a Brighton 
train ; all other signals remaining unchanged : — or to take a 
case somewhat more complex and which is the oldest of the 
codes^ dating as far back as October 29_, 1851^ and provided 
originally for up trains on the half-mile of line intervening 
between Spa Bead and the entrance to the joint station at 
London Bridge — one blow for a Croydon train_, tiuo for a 
Brighton train^ three for a South-Eastern train. 
Another old-established illustration of the manner in which 
bell language,, limited though it is in extent^ can be modi- 
fied to meet the necessities of the case^ is to be found on the 
viaduct extending from London Bridge station to near New 
Cross. There are^ on the west side,, three lines of rails^ one of 
which is used for all down trains^ which consist of trains for 
Dover^ for Brighton, for Epsom, and for the Crystal Palace ; 
one of the lines is used for Dover and for Brighton trains ; 
the other for Epsom and for Crystal Palace trains. Distinctive 
signals are required — one blow on the bell is used for all trains 
down; and tiuo, three, midi four for the up, distinguished into 
three classes ; and on account of the rapidity with which the 
trains, particularly the down trains, follov/ each other on the 
same line of rails, special regulations are in force as to the 
mode of answering and the mode of reporting a train in. 
Also when the down trains are approaching the junction on the 
hither side of New Cross, where the Dover and Brighton trains 
have to be sorted out and turned on to one pair of rails, and 
the Epsom and Crystal Palace on to another pair, the signals 
also are separated and sent on ahead on different wires and bells. 
Heretofore, the illustrations have been mainly confined to the 
cases in which two bells constitute the system; but at junction 
stations, a third bell, and in some cases a fourth, is required. 
They are all properly placed; and their tones and position and 
language are very definite ; and all that has been said above 
applies equally to them. In cases where it is required, a 
counting index is an appendix to a bell, which tells off and 
indicates the bell that has been sounded, and the number of 
blows that have been tiiven. 
