o
reflect light that affects the retina of one person and not the
retina of another? We may reply that the difference must lie in the
retinae, one being more sensitive than the other. But we do not
find the same difference of sensitivity in regard to the light
reflected from ordinary objects. It seems to follow then that the
light reflected from the spirit-hand is a peculiar kind of light,
lying outside the limits of the ordinary visible spectrum. But in
that case, why is not the person with the more sensitive retina
affected by it? For of course all ordinary objects are constantly
giving off radiations outside the limits of the visible spectrum;
but our supposed sensitive apparently does not perceive them."[29]

First, as to the matters of fact. Where is the evidence that those with
the most sensitive retinae were not the very ones who perceived, most
perfectly, the spirit-hand? Were a series of experiments conducted to
show which of the onlookers possessed the most sensitive eyes? If so,
where are these experiments recorded? It is quite possible that the body
is constantly giving off a kind of _aura_--perceptible to some,
invisible to others; and the fact that some do not see it is no proof
that it is not there. If the experiments of Reichenbach and others go
for anything, indeed, there is very good evidence that such emanations
do take place--and I venture to think (however rank heresy this may
appear) that these experiments have never been completely refuted, and
the results obtained shown to be traceable _in toto_ to suggestion. The
eyes of certain individuals might be attuned to receive vibrations or
impressions quite imperceptible to others, no matter how sensitive their
retinae to normal perceptions or sensations.

But, quite apart from such purely "physical" speculations, I can quite
conceive that these hands were not "seen" in the ordinary sense of the
word at all. The physical eyes may have played some part in their
perception, but only a small part. It is quite possible that "hands" of
the character here seen were active and functioning upon another plane
altogether than the sense plane, and were perceived at the time by a
species of _clairvoyance_. What "clairvoyance" is I do not pretend to
know (unless spiritism be true, in which case I can quite easily
conceive its _modus operandi_), but the mass of evidence in its favour
seems to place it quite beyo