o the receiver in wireless telegraphy.
This explanation is so common that many persons accept it without
further ado, as being the correct explanation of the facts. But such a
theory cannot be said to cover the facts in a satisfactory manner.

In the first place, there seems to be no definite or prescribed
area in the brain adapted for such a purpose; no cell or centre has
as yet been discovered which appears destined to send out waves of
this character. Still, perhaps it will be some day, for the functions
of certain portions of the brain--particularly the frontal lobes--are
as yet very little understood. But there is the argument that, if
such waves exist, they must be detected by means of our scientific
instruments--instruments so delicate and subtle that they are able to
measure the difference of the pull of gravity of an article when placed
on the table or on the floor, or can register the heat of a candle at a
distance of more than a mile (Langley's bolometer). Compared with such
delicate instruments, our five senses are coarse indeed, and any
vibrations which can affect these same senses must surely affect the
more delicate and sensitive instruments just mentioned. Yet none of them
have as yet been able to indicate the existence of any such vibrations,
and this would seem to show that they cannot exist.[42]

But there is a reply to this argument. It may be said that, although the
_senses_ do not register any such vibrations, the _brain_ might do so,
in some direct manner; and the brain might be far more sensitive than
any instrument so far devised. Indeed the definition of telepathy, "the
ability of one mind to influence or be influenced by another mind
otherwise than through the recognized channels of sense," would seem to
indicate that in this process only the brain is involved, and not
necessarily the physical senses at all. So far, then, so good; telepathy
might still be vibratory in character.

But if so, how could such waves get through the skull to act upon the
brain direct? This is a staggering thought to the ordinary materialist,
and at first sight renders such an action unintelligible and hence
"impossible"! But to reason thus would be very superficial. For we know
that certain physical energies pass through solid substances--substances
impervious to other physical energies. Thus we know that glass permits
light to pass through it, but is a non-conductor of electricity; while
steel is impervious to li