essure
that the closed lid exerts upon the eyeball, causing a mechanical
excitation of the optic nerve. But the explanation of the phenomenon and
the name that is given to it matters little. It occurs universally and
it constitutes--I may say at once--the principal material of which we
shape our dreams, "such stuff as dreams are made on."

Thirty or forty years ago, M. Alfred Maury and, about the same time, M.
d'Hervey, of St. Denis, had observed that at the moment of falling
asleep these colored spots and moving forms consolidate, fix themselves,
take on definite outlines, the outlines of the objects and of the
persons which people our dreams. But this is an observation to be
accepted with caution, since it emanates from psychologists already half
asleep. More recently an American psychologist, Professor Ladd, of
Yale, has devised a more rigorous method, but of difficult application,
because it requires a sort of training. It consists in acquiring the
habit on awakening in the morning of keeping the eyes closed and
retaining for some minutes the dream that is fading from the field of
vision and soon would doubtless have faded from that of memory. Then one
sees the figures and objects of the dream melt away little by little
into phosphenes, identifying themselves with the colored spots that the
eye really perceives when the lids are closed. One reads, for example, a
newspaper; that is the dream. One awakens and there remains of the
newspaper, whose definite outlines are erased, only a white spot with
black marks here and there; that is the reality. Or our dream takes us
upon the open sea--round about us the ocean spreads its waves of
yellowish gray with here and there a crown of white foam. On awakening,
it is all lost in a great spot, half yellow and half gray, sown with
brilliant points. The spot was there, the brilliant points were there.
There was really presented to our perceptions, in sleep, a visual dust,
and it was this dust which served for the fabrication of our dreams.

Will this alone suffice? Still considering the sensation of sight, we
ought to add to these visual sensations which we may call internal all
those which continue to come to us from an external source. The eyes,
when closed, still distinguish light from shade, and even, to a certain
extent, different lights from one another. These sensations of light,
emanating from without, are at the bottom of many of our dreams. A
candle abruptly lighted in