‘abit _ 






































Aprit 28, 1923] 
dynamics of the Atmosphere” is characteristic, and 
therefore full of new ideas and new views of old ideas. 
_ He treats the atmosphere as a whole as a “ heat 
engine” of the classical type. An indicator diagram 
“of a novel type, in that the co-ordinates are tempera- 
ture and entropy, is constructed, and we are taken 
through a “cycle of operations” which involves a 
return ticket from Java to “the cold slopes of the 
‘mountainous Arctic and Antarctic lands,” and during 
the course of which we realise our entropy like a 
“normal traveller cashes his circular notes, and occasion- 
ally we receive fresh funds from the water vapour 
which we have smuggled in our luggage. Sir Napier 
also introduces us to the “ resilience of the atmosphere,” 
from which “ arises the capacity of a layer of air to 
act as a ‘deck’ or ceiling, preventing any vertical 
‘motion, and therefore limiting the motion of the 
atmosphere to horizontal layers.” The whole article 
‘is stimulating and its value cannot be overrated. 
_ Those of us who are interested in atmospheric 
electricity are feeling more and more the need for a 
good account in English of this branch of meteoro- 
logical physics. There is more than enough material 
for a good-sized book, but the few workers in atmo- 
pheric electricity in this country have other interests, 
and there appears to be no immediate prospect of the 
need being satisfied. We have all the more reason, 
therefore, to be grateful to Mr. C. T. R. Wilson—one 
of the qualified workers who has other interests—for 
his article. There are so many unsolved problems in 
atmospheric electricity that any account of the work 
done and of the theories propounded to explain the 
observations must of necessity exhibit the personal 
opinion of the writer. This article is no exception, 
‘and Mr. Wilson’s point of view is clearly discernible. 
His account is, however, perfectly fair, and as unbiassed 
as it could be in the circumstances. 
Most writers have recently acknowledged them- 
selves defeated in their attempts to explain the main- 
tenance of the earth’s normal electrical field, but Mr. 
Wilson makes it quite clear that in his opinion thunder- 
storms offer a way of escape from this impasse. The 
small amount of evidence which he adduces is not very 
impressive, but until more work has been carried out 
along the lines indicated by Mr. Wilson it will not be 
possible to say that his solution is incorrect. 
_ We began this review with expressing gratitude to 
Sir Richard Glazebrook, and we cannot do better than 
end on the same note. The criticisms we have made 
are of secondary importance and are very much in the 
nature of looking a gift horse in the mouth. But there 
is no objection in examining the mouth if it helps one 
_ to understand the gift and to make the best use of it. 
G. C. Simpson. 
NO. 2791, VOL. 111] 
NATURE 
561 

Climatic Changes. 
(1) The Evolution of Climate. By C. E. P. Brooks. 
Pp. 173. (London: Benn Bros., Ltd., 1922.) 
8s. 6d. net. 
(2) Climatic Changes: their Nature and Causes. By 
Ellsworth Huntington and S. S. Visher. Pp. 
xvi+329. (New Haven: Yale University Press ; 
London: Oxford University Press, 1922.) 17s. 6d. 
net. 
HUNDRED million or a thousand million years 
ago the temperature of the earth’s surface 
was very much the same as now,” say Profs. Hunting- 
ton and Visher in the first chapter of their “ Climatic 
Changes ” (p. 15). This uniformity of climate through- 
out geological time, in contrast with the inconstancy 
of the weather from day to day and from year to year, 
is the great paradox of geological meteorology. The 
climatic conservatism of the earth as a whole is 
qualified by great local changes which have produced 
glaciations at about ten different geological dates and 
acclimatised in high latitudes plants allied to those 
now confined to warmer regions. The study of 
climatic changes has the especial attraction that it is 
a tempting explanation of the fall of civilisations and 
States, since man is obviously dependent on the 
weather. 
(1) The perennial controversy as to whether climatic 
change is due to terrestrial or to celestial causes is 
continued in the two new works by Brooks and by 
Huntington and Visher. While Mr. Brooks main- 
tains that the climatic changes proved by geology can 
be explained by alteration in the distribution of land 
and water, the American authors attribute them to 
occasional changes in the condition of the sun. Mr. 
Brooks in expounding, his conclusion, rejects the 
atmospheric theories based on variations in the amounts 
of carbon dioxide and of volcanic dust, and his verdict 
on this question is given added weight by Dr. G. C. 
Simpson’s testimony, in an introductory note, to his 
authority on meteorology. Mr. Brooks explains the 
last main geological change of climate as due to great 
uplifts of land in high latitudes having enlarged both 
polar glaciers and tropical deserts. He “shows how 
enormously effective the land and sea distribution really 
is,” by calculating what the temperatures on one zone 
on the earth would be if it were composed solely of land 
or were occupied entirely by sea. In a useful appendix 
he provides data by which the effects on temperature 
of variations in land and sea can be calculated. 
Unfortunately, the meteorological sections of Mr. 
Brooks’s work are relatively short, and most of it is 
devoted to accounts of geological and historical varia- 
tions of climate on which the author’s opinions are less 
RI 
