
May 19, 1923] 
NATURE 
669 

_ form’ a closed system or end on boundaries, we shall 
have to assume that in a cyclone the dynamical 
conditions extend from the ground surface to con- 
siderable heights. Perhaps also the entire length 
of the vortex and not simply the length where the 
sustaining energy is supplied is effective in offering 
resistance to extraneous forces, because the energy 
wherever it is supplied will distribute itself over the 
entire length. The high degree of permanence of 
the type of motion is also suggestive that its enormous 
momentum does offer considerable resistance to all 
forces of destruction. A small vertical gradient of 
wind, if there is such a gradient at all, will therefore 
probably not shear a cyclone out of existence. It 
will perhaps deform the cyclonic system or make its 
axis inclined to the vertical; but if the gradient is 
considerable and of long duration, and if the struggle 
to maintain its circulation and to remain reasonably 
erect proves too much for the cyclone, it will 
eventually die. 
The possibility of the axis of a cyclone being 
inclined to the vertical has long been surmised, and 
Sir Napier Shaw himself has advanced arguments 
attempting to give definiteness to the meaning of 
this itea (“Manual of Meteorology,” Part IV., p. 
145). It should, however, be remarked that the 
axis of a cyclone being inclined to the vertical will 
have a definite meaning only if the whirl is supposed 
to extend to heights comparable to the diameter of 
the core and not simply to 3 or 4 km., that is, only 
a little beyond the levels where the sustaining energy 
is supplied, as suggested by some meteorologists, 
including Eliot and Dallas. 
If, on the other hand, we do not consider the 
cyclonic system and the flowing current, if any, as 
two distinct systems, and seek for an explanation of 
the movement of cyclones in the mechanism of the 
2 etapa system itself, then the consideration of the 
shearing of a cyclone due to a vertical gradient of 
wind does not arise at all. Consider, for example, 
the storms which form in the Indian seas. The 
centrifugal force in these storms, especially at the 
outer margin, is not strong enough to keep the 
monsoon winds feeding into them revolving in a 
circular path, with the result that these winds after 
taking a small turn deviate from the circular path 
and carry the cloud ahead of the storms. The 
recipitation and the consequent latent heat set free 
in front of the storms reduce the pressure there, 
necessitating a readjustment and a shifting of the 
isobars. This will in general account for the move- 
ments of these storms. It is, of course, implied in 
this explanation that it is not the general drift of 
winds that makes a cyclone move, but that the 
movements of the cyclone involved in its mechanism 
make the outlying winds adjust themselves to the 
motion. . §. K. Banerj1. 
The Observatory, Bombay, March 27. 

A Levitated Magnet. 
PRESUMABLY all interested in magnetism have tried 
to keep a magnet in suspension, by the repulsion of 
like poles balancing its weight. In common with 
others, I have always failed to do this with steels 
hitherto available. The experiment fails through 
inability of the small magnet to resist having its poles 
reversed, or diminished in strength, by the intense 
field necessary for levitation. 
Recent research on magnetic steels has, however, 
produced steels having the necessary resistance against 
reversal of polarity and with the necessary strength 
of magnetic field. 
NO. 2794, VOL. I11 | 
‘glass enclosure, 
I find that the experiment of flotation can be 
shown by using very simple apparatus. The best 
results have been obtained by using a solid rod of 
special steel, 2 inches by 4, weighing about twelve 
grams. This rod is enclosed in a flat glass cell, 
slightly larger, giving clearance of about 1 mm. 
between the ends and sides, so that the rod may be 
able to move freely. This glass cell should be open 
at the top, and have a vertical height of about 3 
inches. The bottom should also 
be made of thin glass—old photo- 
graphic plates (quarter plates) 
answer very well for making this 
adhesive tape 
being used for joining the glass 
plates, which may be separated 
by flat pieces of wood or glass 
slightly thicker than the steel 
bar, to give sufficient clearance. 
The magnetised rod should rest 
freely on the glass bottom (Fig. 1). 
Holding the cell vertically, it 
is lowered slowly towards the 
poles of a horse-shoe magnet, 
held vertically. If the poles of 
the horse-shoe magnet are of the 
same sign as the opposing poles of 
the magnetic rod, the latter will 
rise and oscillate up and down 
in its enclosure. When properly 
adjusted in the field of a good 
magnet the rod will remain per- 
manently poised about half an 
inch above the poles, which should be about the same 
distance apart as the poles of the levitated magnet. 
Good bar magnets may be used, thus enabling the 
correct separation of the poles to be found experi- 
mentally. 
A much greater distance of separation may be 
obtained by using an electro-magnet. In this case 
the cell must not be placed on the poles before turning 
on the current or the rod magnet will be reversed 
before it has time to rise and it will remain on the 
floor of the cell, being attracted. The same may 
happen if the cell is lowered awkwardly so that only 
one pole of the rod can rise: some reversal then 
takes place, necessitating remagnetisation of the bar. 
The particular steel used by me I owe to the kindness 
of Mr. W. H. Glaser, who tells me it contains 15 per 
cent cobalt and is known as “‘ cobalt chrom ”’ steel. 
F. Harrison GLEw. 
156 Clapham Road, London. 

Fic. 1. 

Science and Economics. 
F. S. M., the writer of the article “‘ Labour and 
Science in Industry,” in his rejoinder to my letter 
(NatuRE, April 14, p. 498) does not seem to grasp 
my main point, that the present economic system 
has no sound physical foundation, and that it was 
an element of physical reality—for example, the laws 
of the creation of wealth as distinct from debt—that 
I wished introduced into the proceedings of the 
Economics section of the British Association. If the 
section has been proceeding on this road for a good 
many years now, as claimed, I apologise. But I am 
surprised at the slow progres it has made. 
My “‘ we,” in the phrase ‘‘ economic system under 
which we perish,” was meant to be fairly catholic, 
and I have no objection to including the Russians 
and Chinese, though I think they may outlast us. 
My information about Russia is largely from school- 
boys, who write to be told the latest about the atom ; 
and about China, that the children work in mills 
U2 
