34 
THE TELEGRAPH. 
low voice at the transmitter are then heard with increased 
distinctness ; and if the apparatus is provided with the before- 
mentioned speaking-trumpet, words pronounced in an ordinary 
tone even at the distance of twelve yards from the transmitter 
may be clearly heard. These effects are really of much inte¬ 
rest, for you can attain the extraordinary result of carrying 
on a conversation without leaving your chair, even when the 
apparatus is several yards off. But your interlocutor must in 
this case speak into, and listen at, the acoustic tube with 
which the apparatus is fitted. 
The Compagnie Generale des Telephones has in no way 
altered this apparatus for public use. Each subscriber has 
of course an instrument fitted up in any room he may wish, 
where someone is constantly present, or is not so far off but 
that the apparatus may always be heard. I shall presently 
explain how in certain circumstances, such as in noisy or 
little-visited places, the difficulty of doing this is overcome. 
At Paris, where this system of lines has been established, 
the subscriber is connected by an insulated conducting wire 
with the central office at No. 66, Rue-Neuve-des-Petits - 
Champs. The lines are at present partly aerial, and partly 
subterranean, passing into the sewers. These lines have been 
constructed by government engineers. 
The insulation of the wires is a very important matter ; for 
it is well known that two lines running side by side, affect 
each other so that the words that are passing in one may be 
heard in the other. This is a serious inconvenience, which 
leaden covers and all other plans that have hitherto been 
proposed have failed to remove. It seems, however, that 
Mr. Gower has succeeded in obviating this by means of a 
particular method of insulation, which is at once secure and 
inexpensive. The wires are of different colours in the several 
cables, as are the cables themselves, so that in case of an 
accident to any line its course may be traced, as for instance 
the blue wire of the black and red cable. When the cables 
reach the central office the bundles are separated, and the 
cables are unwound, the wires being distributed to their 
several places. 
It is here that the difficulties begin, and in order to under¬ 
stand what they are, let us imagine the system at work. For 
