NATURE 
ayer 
THURSDAY, NOVEMBER 20, 1913. 
MODERN PHYSICAL 
IDEAS AND 
RESEARCHES,” __ 
(1) Modern Electrical Theory. By Dr. N. R. 
Campbell. | Second edition. Pp. xii+4oo. 
(Cambridge: University Press, 1913.) Price 
gs. net. j is 
(2) Les Idées Modernes sur la Constitution de la 
Matiére. Conférences Faites en 1912. By E. 
Bauer, A. Blanc, E. Bloch, Mme. P. Curie, 
A. Debierne, and others. Pp.) 370, (Paris: 
Gauthier-Villars, 1913.) Price 12 francs. 
(3) Researches in Physical Optics, with especial 
reference to the Radiation of Electrons. Part i. 
By Prof. R. W. Wood. Pp. vii+ 134 +x plates. 
(New York : Columbia University Press, 1913.) 
(1) HE second edition of Dr. Norman Camp- 
bell’s “Modern Electrical Theory,” re- 
viewed first in NaturE, May 28, 1908, is practi- 
cally a new book. The work of Barkla and Bragg, 
dered necessary a fresh treatment of part ii. 
dealing with radiation. 
and Stark’s work on valency alter completely 
part iii, which deals with electricity and matter, 
a field in which second thoughts have proved 
notoriously less ambitious than the first, whilst the 
first part, which deals with the electron theory 
proper, has also been entirely re-written. 
’ 
It must have been a task of no ordinary magni- | 
tude to attempt to present to-day the changing 
theories of modern physics. Speaking of the 
subject of radiation, the author claims it is. the 
best attempt in the English. language to deal | 
generally with the matter, because ‘‘so far as I 
know there is no other.” Again, in the references 
to the literature at the end of chapter i., after a 
mention of Lorentz's “Theory of Electrons,” we 
read: “I know of no other English treatise which 
can be recommended with confidence,” and the 
remark will be generally endorsed. 
The book deals with the whole of the large legi- 
timate field of the electron theory, electro-magnet- 
ism, metallic and electrolytic conduction, optics, 
radiation, and the chemical as well as physical 
properties of matter. It is in welcome contrast 
to the earlier more or less popular presentations 
of the subject which have appeared in our Jan- 
guage, in that as much attention is given to the 
failures as to the successes of the theory, and in 
that, in the absence of any experimental evidence | 
of positive electricity apart from matter, it does | 
not trespass unduly into the region which many 
ii people have been led to regard as the chief object 
NO. 2299, VOL. 92| 
2 
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The principle of relativity | 
of the electron theory, the explanation of matter 
in terms of the electron. 
Physical theories at the present moment are so 
shaky at the foundations that the doubt arises 
sometimes whether the superstructure is not being 
built up too rapidly. The difficulties, now ten 
years old, in reconciling the undulatory and cor- 
puscular types of radiation in one theory, the 
hopeless confusion that prevails as to the neces- 
sity for the existence of an ether, and the modern 
discrete or quantum theory of energy, seem to call 
for a more drastic reconsideration than we find 
| here of many of the simplest physical conceptions 
and their experimental basis. Take, for example, 
the view that has been universally held of the 
uniform propagation of radiation in all directions 
through space. There seems to be really no evi- 
dence for this. All that experiment and observa- 
tion justify is its propagation between portions of 
space occupied by matter. Elsewhere it may not 
be propagated at all. Recent suggestions that it 
| 1S propagated along ‘‘Faraday tubes” which, 
_ and the theories of Einstein and Planck have ren- | 
starting from the radiator, must necessarily end 
“somewhere,” seem vaguely to imply something 
of the kind. But what a different complexion 
would be assumed by some of the larger general- 
isations of science, in the field, for example, of 
the maintenance of solar and cosmical energy, not 
to mention problems in wireless telegraphy con- 
nected with the curvature of the waves round the 
earth, and all of the topics dealt with in the 
present book, if it were frankly confessed at the 
outset that we are really in complete ignorance as 
to the answer to this simplest first question about 
the nature of radiation. 
In the concluding chapters the author permits 
himself to wander beyond the strict boundary of 
his’ Subject to discuss the principle. of relativity 
and the changes in current ideas required 
from this new point of view. It is at least instruc- 
tive to try to follow a British author attempting to 
reproduce these abstruse conceptions, which as 
yet scarcely anyone in this country professes to 
understand, or at least to appreciate. But the 
exposition is marred by too great an anxiety to 
defend the view from possible objections, and it 
cannot be said that the fundamental or primary 
significance of the principle is made out, or that 
it has been duly correlated with other physical 
conceptions. One remains in doubt whether, if 
not metaphysical, it is not of subjective rather 
than objective importance, a mathematical correc- 
tion to render consistent observations in which the 
velocity of light enters, and which would be, if 
not actually false, at least inoperative were gravi- 
tational action, for example, instead of light em- 
N 
