hanics, and electricity; photo-telegraphy calling for
a knowledge of all these sciences. There are, no doubt, many wireless
workers who are interested in this subject, but who are deterred from
experimenting owing to a lack of knowledge regarding the direction
developments are taking, besides which, information on this subject is very
difficult to obtain, the science of photo-telegraphy being, at the present
time, in a purely experimental stage.

The wireless transmission of photographs has, no doubt, a great commercial
value, but for any system to be commercially practicable, it must be
simple, rapid, and reliable, besides being able to work {2} in conjunction
with the apparatus already installed for the purpose of ordinary wireless
telegraphy.

As far back as 1847 experiments were carried out with a view to solving the
problem of transmitting pictures and writing by electrical methods over
artificial conductors, but no great incentive was held forth for
development owing to lack of possible application; but owing to the great
public demand for illustrated newspapers that has recently sprung into
being, a large field has been opened up. During the last ten years,
however, development has been very rapid, and some excellent results are
now being obtained over a considerable length of line.

The wireless transmission of photographs is, on the other hand, of quite
recent growth, the first practicable attempt being made by Mr. Hans Knudsen
in 1908. It may seem rather premature to talk about the wireless
transmission at a time when the systems for transmitting over ordinary
conductors are not perfectly developed, but everything points to the fact
that for long-distance transmission a reliable wireless system will prove
to be both cheaper and quicker than transmission over ordinary land lines
and cables.

The effects of capacity and inductance--properties inherent to all
telegraph systems using metallic conductors--have a distinct bearing upon
the two questions, how far and how quickly can {3} photographs be
transmitted? Owing to the small currents received and to prevent
interference from earth currents it is necessary to use a complete metallic
circuit. If an overhead line could be employed no difficulty would be
experienced in working a distance of over 1000 miles, but a line of this
length is impossible--at least in this country--and if transmission is
attempted with any other country, a certain amount of submarine ca