AN HISTORICAL STUDY 455 
that the response of the cell is automatic and does not require the interven- 
tion of a human will. Many of these applications were quite feasible in the 
earliest days of photoelectricity ; for relays, which are a necessary element 
of the apparatus, were used in telegraphy. But the attention of inventors 
was so concentrated on the marvellous that they missed the obvious ; the 
earliest reference we have found to any of these simple applications is well 
within the present century ; but it is possible that earlier suggestions were 
made. Serious attempts to exploit these applications only began with the 
formation of Radiovisor Ltd. in 1928. 
‘Two suggestions that constantly recur are to turn on public lighting when 
dusk falls and to detect burglars by their passage across a beam of light. 
But for the first purpose a time switch is really more effective ; and burglars 
are, alas! rather more intelligent than inventors imagine. But some later 
suggestions have proved practicable ; here are a few: The detection of 
black smoke issuing from a chimney, speeding up an escalator when a 
passenger steps on it, detecting pin-holes in metal sheet for motor-car 
radiators, stopping paper-making machinery when the paper tears, counting 
objects of any kind as they pass down a conveyor, making sure that every 
packet of cigarettes contains its card, preventing vehicles from attempting 
to pass under a bridge too low for them, guiding cloth past a knife by which 
it is to be cut. Photoelectrically all these applications are the same ; the 
object to be detected either interrupts or releases a beam of light passing 
across its path; they differ only in the consequences that result from that 
interruption or release; the securing of the necessary consequences is 
merely a matter of ordinary electrical engineering. There are usually other 
methods of achieving the same end ; the cell could usually be replaced by 
a mechanical contact. 
These comparatively dull and trifling applications of photoelectricity are 
of especial interest from the point of view from which we started ; for they 
are the most likely to produce one of the main evils that is now laid to the 
charge of science. Here we have a direct replacement of man by the 
machine ; the replacement sometimes saves waste because machines are 
less irregular, but its object is usually economic ; the machine is cheaper 
and more profitable. Of course there is good as well as evil; to sit in 
darkness watching for holes in an endless strip of brass is not an ideal way 
for a lad or girl to spend the working day ; it is tolerable only because the 
alternative of no work at all, and no pay, is even worse. In dealing with 
this problem scientific foresight i is not required ; the means to replace all 
forms of drudgery by machine operation already exist ; the future has little 
new for us here ; the sole question is whether we can devise a better alter- 
native to drudgery and thus justify the use of the means that lie to our hand. 
That is a political question, concerning which science may provide the 
facts, but can never provide the decision. 
And so our tale ends, very inconclusively and unromantically, as all 
scientific tales must. For science achieves its purpose only when it becomes 
so commonplace that it is taken for granted and becomes part of everyday 
thought and practice. The ultimate aim of science is always to be uninter- 
esting. We hope we have not been too scientific. 
