NATURE 
445 
THURSDAY, JULY (4, 2912. 
STATISTICS OF MAGNETIC CHANGE. 
Studies in Terrestrial Magnetism. By Dr. C. 
Chree, F.R.S. Pp. xii+206. (London: Mac- 
millan and Co., Ltd., 1912.) Price 5s. net. 
(Macmillan’s Science Monographs.) 
HE title of this monograph would enable 
many of those interested in the subject to 
give a shrewd guess at the author’s name. During 
the nineteen years of Dr. Chree’s superintendence 
of Kew Observatory he has published | several 
laborious investigations as contributions towards 
the elucidation of the cause and manner of the 
different periodic variations of terrestrial mag- 
netism. A reasoned résumé of his previous con- 
clusions forms the basis of the present work, 
which also touches on some of Prof. Birkeland’s 
suggestions, and indicates in what directions the 
author looks for further advance. 
We must confess at the outset, however, that 
we look in vain for any touch of picturesque 
imagination to relieve the solemnity of physical 
facts and mathematical analysis, and perhaps 
attract an uninterested reader. The subject is one 
that offers a field for speculation quite as wide as, 
say, the “canals” of Mars; but Dr. Chree is not 
like Prof. Lowell. We cannot imagine the latter 
writing in reference to any of his dicta:—“It will 
probably, however, be generally conceded that it at 
least creates a strong presumption that the 
accuracy attained is highly satisfactory” (p 82). 
We find practically no attempt at any physical 
hypothesis to account for the various phenomena 
that emerge from the scrupulous analysis to which 
the recorded magnetic movements have been sub- 
mitted. Prof. Birkeland’s classification of mag- 
netic storms is quoted without explanation, so that 
we infer that Dr. Chree is not satisfied with it, or, 
at any rate, has not thought it worth while to 
work on those lines. 
The first chapters are elementary and, of course, 
quite sound, explaining the apparatus used for 
obtaining magnetic records and what is meant by 
secular change. Non-cyclic change, on which the 
author has previously laid stress, occupies a 
chapter to itself. There is no hint as to which 
side he would take in the controversy as to 
whether a magnetic storm is the discharge of a 
slowly charged ‘Leyden jar,” or a sudden charge 
which slowly dissipates afterwards. From the 
analogy of certain curious meteorological ‘ 
cyclic” effects, it is probable that the caution here 
is not misplaced. 
Diurnal inequality on 
“non- 
‘ 
“quiet” and “disturbed ” 
] chapters. 
It may be remarked that there is a 
great opening for “personal” error in the want 
of a uniform system of “smoothing” disturbed 
days. The author as usual lays stress on Fourier 
analysis of the diurnal inequalities, but is satisfied 
to leave to the imagination of the reader what the 
physical meaning of the shorter period waves may 
be. Absolute daily range is to a certain extent 
accidental, and seems to add very little to the in- 
formation obtainable from ‘‘smoothed”’ curves, 
but it is quite right to include a chapter on this, 
as data are regularly published by several mag- 
netic observatories. 
Some of the most interesting chapters in the 
book deal with Antarctic magnetic results, and 
several examples are given showing how very 
much more disturbed the Antarctic curves are than 
those of lower latitudes. In some cases Arctic 
curves are also available for comparison. 
There is a chapter on ‘‘Sudden Commence- 
ments,” but Dr. Chree does not deal with the work 
of Mr. Faris on the rate of propagation, in which 
he is probably influenced by the great gulf between 
what he considers the probable accuracy of time 
determination from a magnetogram, and the 
decimals of a second employed by the Americans. 
The latter part of the book is devoted to the 
relations between sunspots and terrestrial mag- 
netism. It is accepted as beyond question that these 
are related phenomena, though it is not so clear 
whether the relation is simply that of “cause ”’ and 
“effect.” It is unfortunate, perhaps, that there 
is nothing approximating to commensurability in 
the various time units involved, the rotations of 
the earth and sun, the revolution of the earth, the 
periods of the moon, and the so-called sunspot 
period. But we must take strong exception to 
the concluding paragraph. The author should 
have known that astronomers have for some years 
been in the habit of classifying sunspots in different 
stages of their life-history, and “active” and 
“quiescent” spots are quite as definite as “quiet” 
days. The spotted area and its conventional 
measure, the “sunspot number,” seem to be 
regarded by Dr. Chree as the last word in sun- 
spot analysis, so that in this particular he is 
apparently behind the times. W. W. B. 
INTRODUCTION TO THE STUDY OF 
HEREDITY. 
Allgemeine Vererbungslehre. By Prof. V. 
Haecker. Pp. x+392. (Braunschweig: F. 
Vieweg & Sohn, rgr11.) Price 14 marks. 
N the last few years there has been, not 
unnaturally, a succession of “Introductions ” 
days, and also on “ordinary ’’ days, fill three more | to the study of heredity, but none better than Prof. 
NO. 2227, VoL. 89] 
T 
