ses
to be light as soon as we diminish its velocity by one ten thousandth
part. Thence flow those natural conjectures, which are well worthy of
experimental examination: all men do not see by the same rays; decided
differences may exist in this respect in the same individual during
various nervous states; it is possible that the calorific rays, the dark
rays of one person, may be the luminous rays of another person, and
reciprocally; the calorific rays traverse some substances freely, which
are therefore called diathermal, these substances, thus far, had been
called opaque, because they transmit no ray commonly called luminous;
now the words opaque and diathermal have no absolute meaning. The
diathermals allow those rays to pass through which constitute the light
of one man; and they stop those which constitute the light of another
man. Perhaps in this way the key of many phenomena might be found, that
till now have remained without any plausible explanation.

Nothing, in the marvels of somnambulism, raised more doubts than an
oft-repeated assertion, relative to the power which certain persons are
said to possess in a state of crisis, of deciphering a letter at a
distance with the foot, the nape of the neck, or the stomach. The word
_impossible_ in this instance seemed quite legitimate. Still, I do not
doubt but some rigid minds would withhold it after having reflected on
the ingenious experiments by which Moser produces, also at a distance,
very distinct images of all sorts of objects, on all sorts of bodies,
and in the most complete darkness.

When we call to mind in what immense proportion electric or magnetic
actions increase by motion, we shall be less inclined to deride the
rapid actions of magnetizers.

In here recording these developed reflections, I wished to show that
somnambulism must not be rejected _a priori_, especially by those who
have kept well up with the recent progress of the physical sciences. I
have indicated some facts, some resemblances, by which magnetizers might
defend themselves against those who would think it superfluous to
attempt new experiments, or even to see them performed. For my part, I
hesitate not to acknowledge it, although, notwithstanding the
possibilities that I have pointed out, I do not admit the reality of the
readings, neither through a wall, nor through any other opaque body, nor
by the mere intromission of the elbow, or the occiput,--still, I should
not fulfil the dutie