eee 
OcToBER 9, 1913] 
clearly displayed, and, although more elementary 
in its treatment, the book is a worthy companion 
of Whittaker’s well-known “History of the 
Theories of Elasticity and the Ether.” An English 
volume of similar scope would be a very desirable 
addition to current text-books. — RSs, Wi. 
LETTERS TO THE EDITOR. 
[The Editor does not hold himself responsible for 
opinions expressed by his correspondents. Neither 
can he undertake to return, or to correspond with 
the writers of, rejected manuscripts intended for 
this or any other part of Nature. No notice is 
taken of anonymous ‘communications. ] 
The Theory of Radiation. 
Tue natural unit of angular momentum postulated 
by Dr. Wiels Bohr, of Copenhagen, in his researches 
on the theory of spectral lines actually exists. It is 
the angular momentum of the magneton. Rejecting 
entirely the idea of magnetic or electric substance, 
the magneton may be regarded as an inner limiting 
surface of the zther, formed like an anchor-ring. The 
tubes of electric induction which terminate on its 
surface give it an electric charge, the magnetic tubes 
linked through its aperture make it a permanent 
magnet. 
I find that the angular momentum of any such 
system, whatever its shape or dimensions, about its 
axis of symmetry is (877V)-*ex. V is the velocity of 
light, € the electric induction over the surface, and » 
the magnetic induction over the aperture. I shall 
~ consider elsewhere the applications to the theory of 
complete radiation, spectral series, and the asym- 
metrical emission of electrons in ultra-violet light. 
Only this need be mentioned. If an electron (charge «) 
be thrown off from a magneton like a speck of dust 
from a flying wheel, then the angular momentum of 
the magneton changes by the amount —1(27/’)-1z. 
This is therefore the angular momentum of the 
ejected electron about the axis of the magneton. 
Taking the velocity of ejection to be proportional to 
the angular velocity in the magneton, we have 
Ladenburg’s result that the energy of the emitted 
rays varies as the frequency. 
Dr. Bohr, by first insisting on the fact that Planck's 
h is an angular momentum, has done something of 
the greatest importance, whatever the ultimate fate 
of his particular interpretation. Dr. Nicholson has, 
I think, used the same idea. 
G. B. McLaren. 
University College, Reading, September 20. 
Stability of Aéroplanes. 
In his experiments on the resistance of the air to 
spheres, M. Eiffel showed that for a certain critical 
velocity for a given sphere the resistance suddenly 
fails. The critical velocity appears to be very different 
for different spheres; e.g. in his paper (Comptes 
rendus, December 30, 1912) the sudden change is 
shown to begin at velocities of 12, 7, and 4 
metres per second for spheres of diameter 16°2, 24°4 
and 330 cm. respectively. 
Suppose we make a triangular frame with one of 
these spheres at each corner and allow the frame to 
fall from a height. It would appear that if the weights 
of the spheres were so adjusted that the frame would 
NO. 2293, VOL. 92] 
NATURE 
165 
maintain a horizontal position for a part of its flight, 
it must reach some velocity at which the equilibrium 
of the resisting forces would be destroyed, and rota- 
tion would ensue, tending to make the frame take up 
a vertical position. 
If such a law holds for bodies of other shapes than 
spheres, it would appear that an aéroplane would have 
a much better chance of being stable in winds of great 
variety of velocities, if the resisting surfaces were all of 
the same size and shape. 
I do not know whether this case has already been 
dealt with by others, and I make the suggestion for 
what it may be worth. 
G. A. SHAKESPEAR. 
The University, Birmingham. 
The Pancreatic Treatment of Tuberculosis and Malaria. 
THERE are two points in Dr. Saleeby’s remarks upon 
p. 61 of Nature (September 18, 1913) which I should 
like to notice briefly. In my letter to you on the 
same page I did not refer to Baetzner’s brilliantly 
successful results in the treatment of tuberculosis by 
pancreatic enzymes (The Practitioner, January, 1913, 
pp- 203-219), because after his prolonged investigations 
the thing is an accomplished fact, which cannot be 
disputed by any interested in its operative treatment. 
I am neither a medical practitioner nor the apostle 
of a new faith, but merely a scientific investigator. 
| foresaw, and foretold, the complete success of this 
treatment of tuberculosis in 1907; and with the fulfil 
ment of this scientific forecast at the hands of Dr. 
M. A. Cleaves in that year and of Dr. W. Baetzner 
more recently, my concern with the matter has ended. 
! Moreover, I have taught medical students for more 
years than I care to think of, and I know how hope- 
less it is to try to teach something new of a scientific 
nature to the medical profession. : 
As to the sexual phases of the life-cycle in malaria, 
they are of no practical importance at all in the treat- 
ment of malaria by enzymes. A reference to Major 
Lamballe’s original manuscript shows that the presence 
of such sexual phases had been verified in several of 
his cases. Like all the clinical symptoms, such as in 
grave cases, delirium and coma, these sexual phases 
vanished and did not return, when the Fairchild injec- 
tions of trypsin and amylopsin were administered. 
These sexual phases, the so-called “crescents,” have a 
scientific interest, but scarcely a clinical importance, as 
Major Lamballe also recognises. The disease is not 
continued by them any more than cancer is continued 
by the cells, to which Prof. Farmer gave the name of 
‘“oametoid tissue.” Probably they are got tid of by 
the leucocytes, but, in any case, in ordinary cir- 
cumstances the pancreatic ferments would be devoid 
of action upon such sexual phases, as my experiments 
upon various non-pathogenic micro-organisms demon- 
strated (vide Beard, J., on the occurrence of dextro- 
rotatory albumins in organic nature, Biol. Ctrlblatt, 
vol. xxxiii., pp. 150-170, 1913). J. Brarp. 
8 Barnton Terrace, Edinburgh, October 1. 
Relative Productivity of Farm Crops in Different 
Countries. 
In view of the repeated statements that British 
farming is declining and that the world is threatened 
with a shortage of wheat supplies, the following 
extract from the results of an investigation into the 
facts regarding both these questions may be of 
interest. Lack of space precludes reference to the 
