APRIL 30, 1914] 
NATURE 21 
Go 
recollection while conducting a course for students. 
But it is perhaps not often that short notes of 
this kind are of very much service to anyone 
except the man who put them together. 
Lessons in Elementary Tropical Hygiene. By 
Henry Strachan. Pp. xi+116+vi plates. 
(London: Constable and Co., Ltd., 1913.) 
Price Is.het. 
WE heartily recommend this little book. It is, of 
course, quite simple and very elementary; that is | 
what it was intended for. Still, London school- 
teachers will find many useful hints in it. But it 
is written chiefly for the help of school-teachers in 
the tropics, both in Africa and in the West Indies. 
The author has been Principal Medical Officer of 
Lagos and of Southern Nigeria, and for two years 
he was acting as Colonial Secretary in Lagos. 
If he does not know the feel of the white man’s 
burden, who does? And he knows well that the 
way to put things right in this world is to get at 
the children. It is they who will hold the ground 
which our men of science have won in the tropics. 
The victories of protective medicine and of sani- 
tary administration over tropical diseases in Africa 
are, to us older people, still new, still wonderful ; 
to the children, before many years are past, they 
will be old stories retold, facts taken for granted. 
Anaesthetics: their Uses and Administration. By 
Dr. D. W. Buxton. Fifth edition. Pp. xiv+ 
477. (London: H. K. Lewis, 1914.) Price 
tos. 6d. net. 
Tue advances in the knowledge of anesthesia and 
analgesia made it necessary for Dr. Buxton to 
rewrite most of the sections in the previous edition 
of his useful work, to delete obsolete apparatus 
and theories, and to add much new matter. 
Among other new features are the procedures in- 
volved in giving nitrous oxide and oxygen in 
major surgery; of ether by the open method, by | 
intra-vascular infusion, by intra-tracheal and 
pharyngeal insufflation, and by colonic absorption ; 
the methods of local regional and spinal analgesia, 
and the employment of alkaloids in analgesia and 
anesthesia. 
Defensive Ferments of the Animal Organism. By 
Emil Abderhalden. Third enlarged edition. 
English translation by Dr. J. O. Gavronsky 
and W. F. Lanchester. Pp. xx+242. (London: 
John Bale, Sons and Danielsson, Ltd., 1914.) 
Price 7s. 6d. net. 
Tue first German edition of this work by the 
director of the Physiological Institute of the Uni- 
versity at Halle a/S. was reviewed in the issue 
of Nature for September 19, 1912 (vol. xc., p. 66). 
That two further editions were published in Ger- 
many in the following year is good evidence of 
the increasing interest being shown in Abder- 
halden’s methods. The English edition will serve 
to bring these researches within the range of 
English students to whom the German text has 
been inaccessible. 
NOL 2322, VOL. 93'| 
LEDTERS 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. | 
Gellular Structure of Emulsions. 
On Prof. Kerr Grant’s letter (p. 162) see for pre- 
vious observations of this striking phenomenon Prof. 
James Thomson, Proc, Glasgow Phil. Soc., February 
15, 1882, reprinted in his collected Papers (p. 136); 
also by reference given in a footnote to the reprint, to 
more detailed and independent investigations by Prof. 
Bénard, of Bordeaux, in Annales de Chimie, 1901, 
and more recent papers, including a recent lecture to 
| the Société de Physique, and to their discussion in 
| connection with the solar phenomena referred to by 
Prof. Grant, by H. Deslandres, in the Annals of the 
Observatory of Meudon (vol. iv., 1910). 
JOsEPH LAaRMOR. 
THE cellular arrangement of convection currents in 
emulsions, described by Prof. Kerr Grant in Nature 
of April 16, was first recorded by E. H. Weber in 
1855, with gamboge suspended in a mixture of alcohol 
and water. It is discussed in O. Lehmann’s ‘“‘ Mole- 
kularphysik.”” The structure is most conveniently 
seen in molten wax or spermaceti, and in this form 
was discovered by H. Bénard. Many papers by 
Bénard, Dauzére, and others have appeared on the 
subject in the Comptes rendus and Journal de 
Physique since 1901, and the possible bearing of the 
_ phenomenon on geological and astronomical problems 
| has been discussed. 
| Dr. Ball upon this writes that I 
| present one.” 
A paper by James Thomson on 
cellular structure due to convection, originally pub- 
lished in 1882, is included in his collected works. In 
this case soapy water was the liquid used. An 
account of the phenomenon, with references, is given 
in the present writer’s report to the Beilby Prize Com- 
mittee, read at the March meeting of the Institute of 
Metals. Ceci, H. DEscu. 
Metallurgical Laboratory, 
University of Glasgow. 
The Origin of the Moon and the Earth’s Contraction. 
In my letter to Nature of February 26, I said that, 
| with the earth’s radius and gravity at their present 
values, and with the speed of rotation assumed to be 
one revolution in five hours, gravitation would exceed 
the centrifugal force until a distance from the surface 
was reached of more than double the earth’s radius. 
‘concluded’ that 
when the moon was detached from the earth, ‘‘ the 
earth’s radius must have been about three times its 
I did not mean to imply this. 
The whole subject of the moon’s origin is highly 
speculative, as Sir G. H. Darwin himself admitted. 
There are two causes that might be invoked to account 
for the separation of her mass from the earth, viz., 
centrifugal force, and the sun’s tidal action. These re- 
quire different speeds of rotation. In Pratt’s ‘‘ Figure 
of the Earth,’ 4th ed., art. 102, he shows that with 
a homogeneous earth the time of rotation which would 
render the centrifugal force equal to gravity would be 
one revolution in two hours and twenty-four minutes. 
I think that if the central parts were the more dense 
the speed would be rather greater. It seems impos- 
sible that a solid crust could have formed at this early 
period, when the spheroid could only just hold to- 
gether. The eccentricity would then have been about 
0:22. 
