The two electrometers were connected together by means of a conductor
(C) passing under the earth, and which at either of its extremities
could be put in communication with either an electric machine or the
ground. A lever handle, J, interposed into the circuit a Volta's pistol,
F, that served as a call.

When one of the operators desired to send a dispatch to the other he
connected the conductor with the machine, and, setting the latter in
operation, discharged his correspondent's pistol as a signal. The call
effected, the first operator continued to revolve the machine so that
the balls of pith should diverge in the two electrometers. At the same
time the two clocks were set running. When the sender saw the word
"attention" pass before the slit in the screen he quickly discharged the
line, the balls of the two electrometers approached each other, and, if
the two clocks agreed perfectly, the correspondent necessarily saw in
the aperture in his screen the same word, "attention." If not, he moved
the screen in consequence, and the operation was performed over until
he could send, in his turn, the word "ready." Afterward, the sender
transmitted in the same way one of the three words, "letters,"
"figures," "dictionary," in order to indicate whether he wished to
transmit letters or figures, or whether the letters received, instead of
being taken in their true sense, were to be referred to a conventional
vocabulary got up in advance. It was after such preliminaries that the
actual transmission of the dispatch was begun. The pith balls, which
were kept constantly apart, approached each other at the moment the
letter to be transmitted passed before the aperture in the screen.

Ronalds, in his researches, busied himself most with the construction of
lines. He put up on the grounds near his dwelling an air line 8 miles
long; and, to do so, stretched fine iron wire in zigzag fashion between