448 PHOTOELECTRICITY, ART AND POLITICS 
being used and incandescent lamps were just becoming practical. But the 
public were apparently more interested in watching the furious dispute 
between Edison and Swan over the priority of their inventions of the in- 
candescent lamp than in considering the worth of what they had invented. 
Communication was the real field of practical electricity. 
It was no accident, therefore, that the first photoelectric cells were a 
bye-product of telegraphy ; but the natural result was that the first thoughts 
for their use were all in the same field. In 1880 the leading inventors are 
Graham Bell with his photophone and Shelford Bidwell, Senlecq and others 
with their systems of telectroscopy, telephotography and the rest. The 
photophone is one of those inventions which are made regularly every few 
years, and as regularly forgotten. The idea is to cause sound to vary a 
beam of light in accordance with its vibrations ; to throw the varying beam 
of light on a photoelectric cell, so as to produce there corresponding varia- 
tions in an electric current ; and to reconvert these variations of current 
into sound by means of a telephone. The scheme is quite practicable, but 
its value was not obvious. It might be used to transmit sounds between 
stations that can be connected by a beam of light, but not by a pair of wires ; 
in other words it would give wireless telephony, restricted to people who 
can see each other ; it might be possible, for instance, between neighbouring 
ships at sea. But even to-day this plan is difficult to carry out except in 
favourable circumstances—and then there are usually better alternatives. 
The other use, also foreseen from the start, is to help the blind. Here the 
first stage is omitted ; the variations in light turned into sounds are not 
those arising from sounds, but such variations as normal people see ;_ they 
are turned into sounds only for the purpose of.those who cannot see. Such 
schemes excited the enthusiasm of Fournier d’Albe some thirty years later ; 
he hoped by this means to enable blind people to read an ordinary page of 
print. A beam of light scans the lines of print and produces sounds in a 
telephone as it passes from black to white and vice-versa ; these sounds are 
determined by the shape of the letter, so that by training the letters can be 
recognised by the sounds. The instrument developed on these lines by 
Barr and Stroud from the ideas of Fournier d’Albe really worked ; but 
alas ! it has proved too cumbrous and expensive to give blind people much 
assistance. 
The other great scheme of the seventies, telectroscopy or telephotography, 
is what we now call picture-telegraphy and take as a matter of course when 
we read our newspapers. Forty years had to elapse before it became really 
practicable ; but the problem was conceived quite clearly and accurately in 
these early days ; methods of scanning and synchronisation, which are still 
the clues to success, were carefully discussed. In some respects the men of 
that time were curiously modern ; for instance they thought of the Kerr 
cell for modulating the light at the receiving end ; most people probably 
regard that as an essentially modern instrument. Indeed they went further 
and envisaged television, realising its possibilities and some of its difficulties. 
Television differs, of course, from picture-telegraphy in that the image has 
to be produced visibly at the receiving end simultaneously with its trans- 
mission and not after an interval during which a picture is produced. 
Ayrton in a lecture on ‘ Seeing by Electricity ’ laid down in 1880 some sound 
principles which workers of our own day have sometimes forgotten, though 
he admitted that they could not immediately be converted into practice. 
The great obstacle to progress in those days was the absence of any method 
of amplifying currents such as we now derive from the thermionic valve. 
Indeed the mere idea of amplification was absent. The last relics of the 
old difference between frictional and galvanic electricity do not seem to have 
