ome the claims of the Page patent
referred to in the preceding narrative. This object was achieved in the
device described in Edison's basic patent No. 158,787, issued January
19, 1875, by the substitution of friction and anti-friction for the
presence and absence of magnetism in a regulation relay.

It may be observed, parenthetically, for the benefit of the lay
reader, that in telegraphy the device known as the relay is a receiving
instrument containing an electromagnet adapted to respond to the weak
line-current. Its armature moves in accordance with electrical impulses,
or signals, transmitted from a distance, and, in so responding, operates
mechanically to alternately close and open a separate local circuit
in which there is a sounder and a powerful battery. When used for true
relaying purposes the signals received from a distance are in turn
repeated over the next section of the line, the powerful local battery
furnishing current for this purpose. As this causes a loud repetition
of the original signals, it will be seen that relaying is an economic
method of extending a telegraph circuit beyond the natural limits of its
battery power.

At the time of Edison's invention, as related in Chapter IX of the
preceding narrative, there existed no other known method than the one
just described for the repetition of transmitted signals, thus limiting
the application of telegraphy to the pleasure of those who might own any
patent controlling the relay, except on simple circuits where a single
battery was sufficient. Edison's previous discovery of differential
friction of surfaces through electrochemical decomposition was now
adapted by him to produce motion at the end of a circuit without
the intervention of an electromagnet. In other words, he invented a
telegraph instrument having a vibrator controlled by electrochemical
decomposition, to take the place of a vibrating armature operated by an
electromagnet, and thus opened an entirely new and unsuspected avenue in
the art.

Edison's electromotograph comprised an ingeniously arranged apparatus in
which two surfaces, normally in contact with each other, were caused
to alternately adhere by friction or slip by reason of electrochemical
decomposition. One of these surfaces consisted of a small drum or
cylinder of chalk, which was kept in a moistened condition with a
suitable chemical solution, and adapted to revolve continuously by
clockwork. The other surface consisted of a