ed for all kinds of
experimental psychology and psycho-physics...."

Sir Oliver Lodge suggested at the time, among other necessary
appliances, a delicate registering balance,--so adjusted that it would
record the medium's weight, unknown to her, at all times during the
seance--the fluctuations in weight, if any, to be recorded on a
revolving drum. Means ought also to be provided for studying the
temperature, pulse, muscular exertion, breathing, etc., etc. The
lighting of the room should be carefully attended to and capable of the
slightest gradation. Means should be provided for obtaining moving
pictures of the seance from without the room, unknown to the medium.
Were the sittings held in complete darkness, these photographs could be
obtained by means of ultra-violet light, with which the room might be
flooded. In addition to these devices, we may add others--such as X-ray
tubes, high-frequency currents and a delicate field of electric
force,--while instruments for testing the ionization of the air (if it
exists) in the immediate vicinity of the medium, during a seance, should
also be employed,--together with the more strictly psychical instruments
and devices which have been utilized of late years.

Electrical apparatus _has_, in fact, been utilized on several occasions
to test so-called "physical mediums" in the past. Italian investigators,
particularly, have excelled in this. In a series of seances conducted in
Naples, the following apparatus was employed. (Fig. 1.)

[Illustration: Fig. 1]

A telegraphic key (b) was connected by wires (a,a) to a battery (d) and
to two screws, connecting them with an electro-magnet (e) to the
opposite end of which was attached a needle. The point of the needle
touched a revolving drum (f), with a smoked surface, driven by two
interlacing, cogged wheels. The whole of this registering apparatus was
enclosed under a glass bell-jar (g). The telegraphic key itself (b) was
covered by a cardboard box (c). The "powers" manifesting were asked to
press the telegraphic key _without_ tearing the cardboard box (that is,
_through_ it). When the key was depressed, this would be instantly
communicated to the electro-magnet, and cause the needle to
oscillate,--these oscillations being marked upon the smoked surface of
the revolving drum. A number of successful tests were conducted by means
of this apparatus.

[Illustration: Fig. 2]

A variation of this was then employed (Fig. 2). A cylinde