in 1553, J. B. Porta cites an experiment that had been made with the
magnet as a means of telegraphing. In 1616, Famiano Strada, in his
_Prolusiones Academicae_, takes up this idea, and speaks of the
possibility of two persons communicating by the aid of two magnetized
needles influenced by each other at a distance. Galileo, in _Dialogo
intorno_, written between 1621 and 1632 and Nicolas Caboeus, of Ferrara,
in his _Philosophia magnetica_, both reproduce analogous descriptions,
not however without raising doubts as to the possibility of such a
system.

A document of the same kind, to which great importance has been attached
is found in the _Recreations mathematiques_ published at Rouen in 1628,
under the pseudonym of Van Elten, and reprinted several times since,
with the annotations and additions of Mydorge and Hamion and which must,
it appears, be attributed to the Jesuit Leurechon. In his chapter on the
magnet and the needles that are rubbed therewith, we find the following
passage.

"Some have pretended that, by means of a magnet or other like stone,
absent persons might speak with one another. For example, Claude being
at Paris, and John at Rome, if each had a needle that had been rubbed
with some stone, and whose virtue was such that in measure as one needle
moved at Paris the other would move just the same at Rome, and if Claude
and John each had an alphabet, and had agreed that they would converse
with each other every afternoon at 6 o'clock, and the needle having made
three and a half revolutions as a signal that Claude, and no other,
wished to speak to John, then Claude wishing to say to him that the king
is at Paris would cause his needle to move, and stop at T, then at H,
then at E, then at K, I, N, G and so on. Now, at the same time, John's
needle, according with Claude's, would begin to move and then stop at