SEPTEMBER 18, 1913] 
‘NATURE 
59 
numerically of the order of 1000 in that region, 
but Ap/p cannot be neglected in calculations re- 
quiring greater accuracy, or in the upper reaches 
‘of the atmosphere, where p has a much smaller 
value because @ does not fall proportionally to the 
fractional fall of p. 
In considering any physical explanation of the 
structure of the atmosphere, the difference 
“Ap/p—Aé/6@ is an important quantity. In fact, 
as a rule, it appears that, somewhere or other 
in a vertical section of the troposphere (where A@ 
and Ap are of the same sign), in consequence of 
the variations in the magnitudes involved, the 
quantity Ap/p—Aé@/@ becomes sero and changes 
_ sign. To that curious circumstance is due the 
dominance of the influence of the stratosphere 
“upon the dynamics of the surface layers, although 
it only represents about a quarter of the whole 
“mass of the atmosphere. In the stratosphere Ap 
d A@ are of opposite signs, and their influences 
in the production of pressure difference reinforce 
each other. Hence in the stratosphere, pressure 
‘differences are rapidly built up, while in the 
troposphere changes are capricious and contra- 
-dictory. 
_ But fortunately these considerations are, so far 
_as can be judged, of little importance in the cases 
_to which Mr. Cave has applied his rough and 
ready formula, and do not affect the general 
accuracy of his conclusions. 
_ For the practical study of the dynamics of the 
atmosphere we are largely dependent upon 
observations with pilot balloons. They may be 
taken as supplementing observations of clouds, 
and, in due time, both must be brought into 
relation with the observations of pressure and 
temperature obtained from registering balloons. 
It is in many ways unfortunate that the track 
of a registering balloon cannot always be followed 
by a theodolite or otherwise determined. As it 
is, we often get our kinematical conditions from 
One occasion, and our baric and thermic conditions 
from a different one. 
Something may be done to bring the two 
together by means of observations of cloud- 
sequence, which can be observed on either occa- 
sion. At present these have hardly come within 
the range of meteorological work. Few observers 
are effectively conscious of the rapidity of the 
changes which are indicated by clouds, and which 
“must be the results of the distribution of pressure, 
temperature, and wind. 
In the book before us little is said of the 
association of cloud-forms and cloud-changes with 
the variations of the structure of the atmosphere 
isclosed by pilot balloons, but that part of the 
“subject has great possibilities, and this leads us 
NO. 2290, VOL. 92] 
a 
: like. 
to express the hope that in a subsequent edition 
of this interesting work Mr. Cave may be able 
to give us the benefit of his experience in that 
direction also. W. N. SHaw. 
SOCIOLOGY AND MEDICINE. 
(1) The Task of Social Hygiene. By Havelock 
Ellis. Pp. xv+41q4. (London: Constable and 
Co., Ltd. 1912.) Price 8s. 6d. net. 
(2) The People’s Medical Guide: Points for the 
Patient, Notes for the Nurse, Matter for the 
Medical Adviser, Succour for the Sufferer, Pre- 
cepts for the Public. By Dr. John Grimshaw. 
Pp. xx+839. (London: J. & A. Churchill. 
1912.) Price 8s. 6d. net. 
(2) "ee title of this book somewhat masks 
the nature of its contents, for by “social 
hygiene” the author means to convey the study 
of those things which concern the welfare of human 
beings living in societies. The various chapters, 
or essays as they practically are, include such 
varied subjects as the changing status of woman 
and the woman’s movement, eugenics and love, 
religion and the child, the falling birth-rate, 
sexual hygiene, war against war, international 
language, and others. The author generally pre- 
sents the two points of view, supporting them by 
quotations and summaries from many sources. 
The essays are interesting reading, but at the end 
leave us somewhat in doubt as to what would be 
for the best, or what the writer considers would 
be best. 
(2) This book covers almost the whole range 
of subjects comprised within the scope of the 
practice of medicine and surgery, including the 
specialities such as diseases of the throat and eye. 
The information given seems generally to be 
accurate, is imparted in simple language, and im- 
portant points are frequently driven home by some 
terse sentence, e.g. “a tooth in the head is worth 
two on the plate” (p. 57). Some capital sections 
are given on the management of children, diets 
and cooking, and physical exercises. The matter 
does not always seem to come quite in the right 
place, and simple domestic remedies and treatment 
may be omitted; for example, that common com- 
plaint of children, “child crowing,” or “spas- 
modic croup,” is scarcely noticed under children’s 
ailments, but is relegated to the chapter on 
diseases of the throat, and it is certainly by ne 
means “invariably” associated with rickets. 
We think that the compass of the work is some- 
what beyond that necessary or desirable for the 
general public, but the volume would serve as an 
excellent book of reference for the district nurse, 
health visitor, missionary, ship’s captain, and the 
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