uction of the shortest Electric Waves
known but also to the construction of a very delicate 'Receiver' for the
detection of invisible other disturbances. The most sensitive form of
detector hitherto known was the "Coherer." One of the forms made by Sir
Oliver Lodge consisted simply of a glass tube containing iron turnings,
in contact with which were wire led into opposite ends of the tube. The
arrangement was placed in series with a galvanometer and a battery; when
the turnings were struck by electric waves, the resistance between loose
metallic contacts was diminished and the deflection of the galvanometer
was increased. Thus the deflection of the galvanometer was made to
indicate the arrival of electric waves. The arrangement was, no doubt, a
sensitive one, but, to get a greater delicacy, Dr. Bose used, instead
of iron turnings, spiral springs which were pushed against each other by
means of a screw.[10] Still the arrangement laboured under one great
disadvantage. The 'receiver' had to be tapped between each experiment.
So something better than a 'cohering' receiving was needed--something
that was self-recovering, like a human eye. To discover that something,
Dr. Bose began a study of the whole theory of 'coherer action.' It was
hitherto believed that the electric waves, by impinging on iron and
other metallic particles in contact, brought about a sort of fusion--a
sort of 'coherence'--and that the diminution of resistance was the
result of that 'coherence.' To satisfy himself as to the correctness of
this theory, Dr. Bose engaged himself in a most laborious investigation
to find out the action of electric radiation not only on iron particles
but on all kinds of matter and ultimately discovered the surprising fact
that, though the impact of electric waves generally produced a
diminution of resistance, with _potassium_ there was an _increase_ of
resistance after the waves had ceased.[11] This discovery at once showed
the untenability of the old theory and pointed to the conclusion that
the effect of electric radiation on matter is one of discriminative
molecular action--that the Electric Waves produced a re-arrangement of
the molecules which may either increase or decrease the contact
resistance. It may be incidentally mentioned here that this detection of
molecular change in matter under electric stimulation has given rise to
a new theory of photographic action.

As a result of his painstaking investigation on the acti