ther
wireless work, has been possible in connection with the practical side of
the wireless transmission of photographs, yet, now that the prospect of
experimental work is once again occupying the minds of all wireless
workers, advantage has been taken of a reprint of this little volume to
amplify a few points that were insufficiently dealt with in the first
edition, and also to add some fresh matter.

To Chapter V. has been added a short description of the Nernst lamp, and
also some useful information regarding photographic films, and a few notes
relating to enlarging included in the Appendix B.

A fresh appendix dealing with the principles of optical lenses has also
been added. This is a subject that plays an important part in any system of
wireless photography, and to those experimenters whose knowledge of optics
is limited this section should prove useful.

To serious workers engaged on the problem of the wireless transmission of
photographs, attention {vi} is called to a series of articles which are
being published from time to time in the _Wireless World_, on the design
and construction of wireless photographic apparatus.

M. J. M.

MAIDSTONE, 1919.

{vii}

PREFACE

In these progressive times it is only reasonable to expect that some
attempt would be made to utilise the ether-waves for other purposes than
that of telegraphic communication, and already many clever minds are at
work trying to solve the problems of the wireless control of torpedoes and
airships, wireless telephony, and, last but not least, the wireless
transmission of photographs.

It may seem rather premature to talk about the wireless transmission of
photographs at a time when the ordinary systems are not fully developed;
but the prospects of wireless photography are of a very encouraging nature,
especially for long over-water distances, as there are great difficulties
to be overcome in long-distance transmission over ordinary land lines and
cables which will be entirely eliminated by wireless methods.

From a perusal of Chapter I. the reader will be able to understand
something of the difficulties that are to be encountered in working over
long distances, and he will also be able to appreciate something of the
advantages that would be derived {viii} from a reliable wireless system.
Apart from the value of such a system for transmitting news pictures, it
would also be of great advantage to transmit to ships at sea photographs of
cr