ize according to the number of
subscribers in them. Where the telephones are thickly installed the
districts are smaller than in sections that are more sparsely settled.

Then all the telephone wires of a certain district converge at a central
station, and each pair of wires is connected with its own particular
switch at the switchboard of the station. That is simple enough; but
when you come to consider that every subscriber must be so connected
that he can be put into communication with every other subscriber, not
only in his own section but also with every subscriber throughout the
city, it will be seen that the switchboard at central is as marvellous
as it is complicated. Some of the busy stations in New York have to take
care of 6,000 or more subscribers and 10,000 telephone instruments,
while the city proper is criss-crossed with more than 60,000 lines
bearing messages from more than 100,000 "'phones." Just think of the
babel entering the branch centrals that has to be straightened out and
each separate series of voice undulations sent on its proper way, to be
translated into speech again and poured into the proper ear. It is no
wonder, then, that it has been found necessary to establish a school for
telephone girls where they can be taught how to untangle the snarl and
handle the vast, complicated system. In these schools the operators go
through a regular course lasting a month. They listen to lectures and
work out the instructions given them at a practice switchboard that is
exactly like the service switchboard, except that the wires do not go
outside of the building, but connect with the instructor's desk; the
instructor calls up the pupils and sends messages in just the same way
that the subscribers call "central" in the regular service.

At the terminal station of a great railroad, in the midst of a network
of shining rails, stands the switchman's tower. By means of steel levers
the man in his tower can throw his different switches and open one track
to a train and close another; by means of various signals the switchman
can tell if any given line is clear or if his levers do their work
properly.

A telephone system may be likened, in a measure, to a complicated
railroad line: the trunk wires to subscribers are like the tracks of the
railroad, and the central station may be compared to the switch tower,
while the central operators are like the switchmen. It is the central
girls' business to see that connec