428 
NATURE 
is the most convenient unit for stating barometric | 
pressures, is 1 leogram per sq. .cm. The c.g.s. unit 
of pressure is the microbar, which is equal to 1 leo- 
milligram per sq. cm. 
Prof. McAdie, in the issue of Nature of March 10, 
1914, referred to the use by chemists of the word bar as 
a name for this c.g.s. unit of. pressure. The bar of 
the chemist is the millionth part of the unit, men- 
tioned in the last paragraph, which has been taken 
into use by Bjerknes and other meteorologists under 
that name. I do not wish to discuss here the merits 
of the question raised by Prof. McAdie. It is perhaps 
a matter for some international assembly attended by 
representatives of both chemistry and meteorology. 
Coming now to units ot work, we see that there is 
no difficulty in defining the leogrammetre as the work 
done by a leogram when its point of application moves 
through a metre. Names of this sort can be used 
in explaining the terms which are in use already for 
quantities of energy. Thus the leomilligramcenti- 
metre is identical with the erg, the c.g.s. unit. The 
theoretical unit of electric energy, the joule, is 1 leo- 
kilogramdecimetre, whilst the commercial, or “‘ Board 
of Trade’ ‘unit, defined’ as 1 kilowatthour, is 
3600 x 1000 joules, or 360 Jeotonmetres. 
Finally, we have to consider units of gravitational 
potential. The usual. definition of potential is poten- 
tial energy per unit of mass. The change of poten- 
tial of 1 gram moved through one metre against a 
field of force sufficient to produce in it.an acceleration 
one leo is one leogrammetre per gram, or briefly, one 
leometre. The difference in potential between two 
horizontal surfaces a metre apart depends on the lati- 
tude; it is o-9780 leometre at the equator, and 0-9832 
leometre at the poles. 
The name leometre is proposed as an alternative to 
Prof. Bjerknes’s ‘‘dynamic metre”; accordingly, it 
may not be out of place to conclude this letter by 
quoting the professor’s note from the Quarterly 
Journal of the Royal Meteorological Society :— 
‘““Names may be attacked from many points of 
view, and, even if left in peace during six years, they 
may be attacked in the seventh. Therefore a change 
in terminology contains a great risk. Still, I am 
willing to take the risk, if some guarantee can be 
obtained securing the prospects of. the new ter- 
minology. I therefore take this opportunity to re- 
quest everyone intending to attack the ‘ leometre’ not 
to postpone the’ attack, but to execute it at once.” 
F.- J.:W. WiaHiprce. 
Meteorological Office, South Kensington, S.W. 
Aristotle’s Physics. 
THE review of Prof. Duhem’s new book, ‘Le 
Systeme du Monde,” over the initials, J. L. E. D., in 
NaturE of May 28, contains what purports to be a 
correct and intelligible summary of  Aristotle’s 
dynamics. It begins with the surprising words, ‘In 
his dynamics the idea of. mass* does not enter,’ and 
speaks loosely of motion as though Aristotle was 
treating of a varying velocity. 
Sir George Greenhill and I both wrote to you on 
January 2, 1914 (vol. xcii., p. 584), pointing out that 
Aristotle throughout treats only of the motion of pro- 
jectiles, and of that only in a resisting medium, and 
then only of that part of the vertical motion when 
the projectile has attained that constant speed known 
to ballisticians as “terminal velocity,” which can be 
as readily observed in rising smoke as in falling rain. 
The equation on which Aristotle really bases his 
ballistics is :— 
fe ae = 
J (22 t 
NO; 2330, VOU" O23] 
a a 
[JUNE 25, 1914 
where H is the Newtonian terminal velocity, w is the 
weight of the projectile, A is the cross section of the 
projectile, + is the density of the medium, k is the 
coefficient of shape. 
In modern ballistic tables we write for the unit 
projectile :— 
pau 
g 
Aristotle put equal to unity. 
We now know that there can be no simple equation 
for vertical motion in a resisting medium except by 
assuming that n=I or 2. 
Whilst he was in England last week for the Roger 
Bacon celebrations at, Oxford, I mentioned this sub- 
ject to Father David Fleming, O.F.M. He gave me 
permission to say that during his tenure of the chair 
of philosophy at the Franciscan House of Studies in 
the University of Ghent, he taught the equation as | 
have given it as the obvious and only true meaning 
of Aristotle’s own words. J. H. Harvucast ie. 
Phenomena of the Conscious and Unconscious. 
Nor very long ago the province of psychology was 
supposed to be confined to the study of the phenomena 
of consciousness. Recently, however, its narrow 
limits have been allowed to be transcended; but even 
now the vast majority of psychologists is so exclu- 
sively occupied in inquiring into the effect of the 
conscious on the unconscious that scarcely any amount 
of justice has been done to the study of the influence 
of the unconscious on the conscious. Yet this latter 
inquiry is by no means insignificant. In fact, it 
counts for more and more. It is not merely that some 
actions, unconscious in the beginning, gradually become 
conscious through the constant interference of volition, 
and vice versa. It is that the entire range of con- 
scious activity is in essence reflex. The conscious, 
which is the superstructure of our mental life, has 
for its underground substratum the unconscious which 
moulds its shape and guides its course. Thus the con- 
scious, which, superficially viewed, seems to control 
and modify reflexes is, in fact, itself a species of 
reflex, 
The bare statement of this doctrine may look rather 
crude; but the grounds which substantiate it are 
rather of a speculative nature, and to dwell on them 
would not be quite appropriate in this journal. My 
aim, however, is different. I am not unaware of the 
rival theory which maintains that all human actions 
are essentially voluntary and have become reflex only 
by practice in the lifetime of the individual or of the 
race. What I desire by publishing this letter in NaTuRE 
is to elicit the opinions of physiologists as to the merits 
of the latter theory. To expect exact scientific evidence 
here is, of course, absurd. But are there even the 
remotest indications in the human and animal 
organism that favour this theory ? 
ApBpuL Majrp. 
Gola Gunj, Lucknow, India. 
THE NATIONAL PHYSICAL LABORATORY 
IN 1913-14. 
© eee annual report of the National Physical 
Laboratory for 1913-14 was presented to 
the general board at the visitation day of the 
Royal Society on June 19. The report forms 
another and a conspicuous testimony to the 
remarkable growth of the laboratory and the 
importance and volume of the work with which 
