we shall be able to receive pictures
from America with as great reliability and precision as we now receive
messages.

In nearly all wireless photographic systems devised up to the present the
chief portion of the receiver consists of a very sensitive galvanometer,
and although very good results have been obtained by their use they are
more or less a nuisance, as the extreme delicacy of their construction
renders them liable to a lot of unnecessary movement caused by external
disturbances. A galvanometer of the De' Arsonval pattern, used by the
writer, was constantly being disturbed by merely walking about the room,
although placed upon a fairly substantial table; and for the same reason it
was impossible to attempt to place the driving motor of the machine on the
same table as the galvanometer. For ship-board work it will be evident that
the use of such a sensitive instrument presents a great difficulty to
successful working, and a good opening exists for some piece of
apparatus--to take the place of the galvanometer--that will be as sensitive
in its action but more robust in its construction.

* * * * *

{74}

CHAPTER V

THE "TELEPHOGRAPH"

In the present chapter it is proposed to give a brief description of a
system of radio-photography devised by the author, and which includes a
greatly improved method of transmitting and receiving, as well as an
ingenious arrangement for synchronising the two stations; the whole being
an attempt to produce a system that would be capable of working
commercially over fairly long distances.

The system about to be described, and which I have designated the
"telephograph," is the outcome of several years' original experimental
work, many difficulties that were manifest in the working of the earlier
systems having been overcome by apparatus that has been expressly designed
for the purpose.

In any practical system of radio-photography the following points are of
great importance: (1) the speed of transmission; (2) the quality of the
received picture; (3) the method of synchronising {75} the two machines so
that transmission and reception begin simultaneously; (4) the correct
regulation of the speed of the driving motors; (5) the simplicity and
reliability of the entire arrangement. Points 1 and 2 are dependent upon
several factors; the number of contacts made by the stylus per minute; the
size of the metal print used; the number of lines per i