44 
THE TELEGRAPH . 
randum on to a third clerk to attend to a particular commu¬ 
tator called “ the great commutator.’ 7 This third clerk estab¬ 
lishes a connection between groups a and c, through line 6, 
and the two subscribers are able to converse together. When 
they have finished they give the signal, and all the pegs are 
taken out and replaced in the line “ terreP 
Fig. 13 is a general view of the central office, containing 
Fig. 15. 
these apparatus, showing the boxes in which the clerk in charge 
of each group is placed, and the apparatus under his control. 
At the further end of the apartment is the “ great com¬ 
mutator. 
In April 1880, there were in Paris fifty lines in use, and the 
Compagnie Generale ties Telephones was about to establish 
systems in other great centres. At that time the use in France 
of telephonic communication was confined to Paris ; while at 
the same period there were in the United States eighty-five 
cities making use of the telephone. At Chicago there were 
