
Marcu 17, 1923] 
“In assuming responsibility for the Index the 
Council of the Library Association was actuated by 
_ the following considerations : 
. “(1) That, in view of the rapid growth of the periodi- 
cal press, the analytical indexing of periodicals could 
be carried out with due regard to efficiency and econ- 
omy only by co-operative effort. 
_ ‘*(2) That such co-operative publication should be 
controlled by a British professional body rather than 
be left to the enterprise of a foreign publisher. 
“(3) That the Index should be compiled by trained 
library workers on a voluntary basis, and that the 
price should be fixed as nearly as possible to the cost 
of production, and without any idea of profit.’’ 
_ Every effort will now be made to bring the Subject 
Index up to date. We hope to complete the 1920 
Class Lists this summer and commence the publication 
of the 1921 Lists in the autumn. For further particu- 
lars application should be made to the Hon. Secretary 
of the Library Association, Westminster Public 
Libraries, Buckingham Palace Road, S. W. 
E. W. Hume, 
Editor of “ The Subject Index 
to Periodicals.”’ 
Gorseland, North Road, Aberystwyth, 
. February 23. 

Time Relations in a Dream. 
I HAVE read with much interest Dr. Atkin’s letter 
in Nature of January 27, and also Mr. Barcroft’s 
letter in the issue of October 23, 1919 (vol. 104, p. 154) 
to which he refers. My own observations, made in 
various degrees of semi-consciousness, appear to 
show that there is no such thing as a definite time 
relation, as it depends entirely on the degree of 
consciousness, the time scale being enormously 
shortened in the semi-conscious state most remote 
from wakefulness, so that the images produced by 
the mind must succeed one another with extra- 
ordinary rapidity when in that state. As wakeful- 
ness increases, the time scale seems to expand, and 
the succession of events proceeds more and more 
slowly, until it practically stops or becomes normal 
as wakefulness resumes absolute control. I have 
been led to believe that the mind is always active 
—just like the heart always pulsates—whether we 
are pee or awake, and that control and memory 
are the features of our waking condition, so that 
we do not remember the images it calls forth, except 
when we are beginning to awaken, and the degree 
of activity of our memory in our dreams and the 
extent of the dream memorised merely depend on 
the rapidity with which we reach wakefulness. 
I have made a number of observations of hypno- 
pompic pictures, or optical illusions, which occur 
while sinking into slumber or during gradual awaken- 
ing. I described my first observations in the Journal 
of the Society for Psychical Research for April 22, 
1921, but since then I made several curious observa- 
tions, some of which concern the case in point. 
The hypnopompic pictures which I have observed 
are generally landscapes passing slowly before one’s 
closed eyes, when in an almost awake condition, one 
being fully aware of one’s wakefulness, and having 
one’s ful] reasoning powers while the illusion proceeds, 
so that one can make precise observations and experi- 
ments as to the effect of volition, etc. The pictures, 
which are extraordinarily sharp and full of detail, 
= mg as an endless panoramic band or film passing 
slowly before one’s mind’s eye, so to speak. The 
film may pass ia any direction, right to left, or the 
reverse, or vertically downwards, or obliquely. A 
film may snap, but it invariably slows down as 
NO. 2785, VOL. 111] 
NATURE 

361 
consciousness increases, till it becomes motionless 
and then gradually fades. 
It seems as if several such bands or films could 
exist at the same time, passing one in front of the 
other, and sometimes in different directions, the 
uppermost alone being visible of course, and its 
sudden ending by snapping allowing the one under- 
neath to be visible. This would explain the sudden 
changes which are often noticed in dreams. The 
fact that the film is panoramic (and not cinemato- 
graphic, that is, without perception of translation) 
is remarkable, as one would have expected it to be 
cinematographic in character. Once, attaining con- 
sciousness very rapidly, I glimpsed, for a couple of 
seconds, a blurred mass of lines such as one sees 
from an express train on a wall quite close to the 
track—lines caused by the persistence of vision 
of the details on the wall, combined with their motion 
relatively to the train. I have no doubt whatever 
that I had witnessed the hypnopompic “‘ film ’’ nearly 
at its normal speed, but with a mind already “ slowed 
down ”’ by the return to consciousness, and unable 
to cope with its speed and see the details which 
otherwise I am persuaded—by the agreement of all 
my observations—would have been visible. 
The latter observation bears directly on the 
question of duration. At such a high translation 
speed, hundreds of times faster than the usual 
speeds I had hitherto observed, a whole panoramic 
view must pass in an extraordinarily short time. 
Moreover, at such a speed, cinematographic effects 
are possible, but I fail altogether to imagine by what 
mechanism they could take place, and so far my 
observations have given me no Clue, although I have 
once or twice witnessed variations in the process 
which prevent me from despairing of getting further 
insight into this mysterious working of our minds. 
It seems as if control and memory slowed down the 
working of the mind so that the speed of succession 
of the images is an inverse function of the degree 
of wakefulness. M. GHEURY DE Bray. 
40 Westmount Road, Eltham, S.E.o, 
February 10. 

The Social Influence of Science. 
In his article in NATuRE of February 17, p. 209, 
Mr. F. S. Marvin says: ‘“‘ When in the sixteenth 
century the mind of Ancient Greece awoke again . . .”’ 
The advent of modern science is here considered as 
a revival and continuation of Greek knowledge ; an 
opinion very commonly held, but entailing some 
difficulty—a millenary period of stagnation and even 
retrogression. This is inconceivable; the very 
essence of science is progress, continuous but not 
steady, because the rate is increasing. This charac- 
teristic of science was pointed out in the Harveian 
Oration for 1897 by Sir William Roberts (‘‘ Science and 
Modern Civilisation,’’ NATURE, October 28, 1897, vol. 
56, p. 621). 
Antiquity has been artistic, literary, philosophical 
with deductive reasoning ; but is markedly deficient 
in the objective study of Nature and the inductive 
mentality. The philosophers’ knowledge of things 
was part of their system, based on a priori principles. 
Their opinions were many and conflicting, with 
various degrees of credulity, a few of them by chance 
right. The influence, if any, on the birth and growth 
of modern science has been very limited ; the method 
of working, by patient observation and experiment- 
ing, is exactly the reverse. The rise of the experi- 
mental inductive method was like a botanical muta- 
tion and inaugurated a new era in the evolution of 
mankind. Ap. K. 
Antwerp, February 17. 

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