APRIL 21, 1923] 






































communications, weapons, archery, etc., involved a 
knowledge of man’s endurance, food consumption, 
horses, shoe leather, the elastic qualities of yew, the 
flight path of arrows, and the like, but then, unlike 
to-day, every member of the governing staff was 
easily an adept in these matters, competent to select 
and profit by any expert specialisation—when for a 
‘spell generals commanded the fleet they were soon 
discovered not to be adept and the sea was entrusted 
to those who were. In both cases it was unnecessary 
to provide a seat on the council for the astrologer, 
alchemist, or magician of the time. To-day, however, 
all this is changed. 
It is not to be expected that even a carefully chosen 
ind widely informed scientific member of council can 
know ballistics, meteorology, chemistry, metallurgy, 
e thermodynamics of the petrol engine, the intricacies 
sound detection, or of wireless procedures, the 
ability of ships, the phugoids of aeroplanes, the 
ary derivatives of their equations of motion, etc. ; 
ut given a really sound scientific representative none 
of these subjects is to him what most of them are to 
the Army Council, Admiralty, and Air Force Council— 
at the best, jargon: at the worst, stupidity. Such 
‘a man would and could seek advice, because he knows 
enough of the problem and of the outlook of science 
see that it was wanted. He could take advice 
because he would know enough to sift it, test it, select 
it, and present it for consideration to a council with 
e real purpose and personalities of which he would 
be acquainted. 
_ How can we make such a need be felt by the war 
achine, which is certainly not asking our advice 
about it? Only by public opinion; and clearly this is 
difficult. Scientific opinion deserves better regard and 
esteem than it gets, and it suffers this loss because of 
the quite unreasonable contempt with which it views 
‘the operations of politicians. - The world of science 
abstains from making its voice heard in the only way 
it can be heard, through the megaphone of the politician, 
_ by reason of the pressure of its organisation. It has 
‘itself no organisation. Some of the wiser men, who 
lifted their heads from the absorbing interest of their 
own grindstones, did in fact form a Conjoint Board of 
_ Scientific Societies, which died a month ago. This body 
_ comprised the leading Institutions and Societies in the 
British Isles concerned with pure and applied science. 
- It might have leavened the lump, and reminded the 
technical world that it is an organic part of modern 
social organisation. Let us hope, as taxpayers, if 
_ from no higher motive, that science and technology 
_ may yet form a federation to promote recognition of 
_ their significance in the affairs of the State. 
Mervyn O’Gorman. 
NO. 2790, VOL. 111] 
NATURE 
523 

The Structure of the Atom. 
The Theory of Spectra and Atomic Constitution : Three 
Essays. By Prof. Niels Bohr. Pp. x+126. (Cam- 
bridge: At the University Press, 1922.) 7s. 6d. net. 
“| HE beautiful conception which inspires and 
co-ordinates practically the whole of modern 
atomic physics is the atomic model of Rutherford and 
Bohr. Its essential feature—the nucleus—was first 
put forward by Rutherford in r91z on the basis of 
experiments on the scattering of a-particles. So con- 
vincing is this model that after only twelve years it is 
known no longer as “ the atomic model of Rutherford 
and Bohr,” but is simply taken for granted as “ the 
atom.” In this development, moreover, the ideas of 
Bohr have played such a dominating part that it is 
of the greatest importance that the three essays of this 
volume should be accessible in English, as well as in the 
original Danish and German, to the widest circle of 
readers. We welcome most heartily their opportune 
appearance. 
When a theory such as the present is expounded 
semi-historically by its principal creator, a critical 
account of the theory itself is scarcely the function of 
a review. Such a critical discussion could be nothing 
less than an exhaustive survey of the whole tendencies 
of modern physics. It is perhaps a less impossible— 
certainly a more relevant—task to attempt to bring to 
notice the various stages of the theory represented by 
the three essays in this book, in the hope that some faint 
reflections of their beauty and convincingness may be 
conveyed to those whose studies are directed elsewhere. 
Some preliminary remarks of a general nature may 
not be out of place. Though the theory itself finds a 
place for much advanced mathematical analysis and 
demands the development of new and more powerful 
weapons than those yet available, in the hands of Bohr 
it is never an abstraction divorced from contact with 
physical realities. Rather he succeeds in bringing it 
ever into closer contact, and expounds it in these essays 
in a simple non-mathematical way which should be 
capable of being followed by any one who is prepared to 
accept the mathematical theorems on which the work 
is necessarily based. The mathematician will desire 
to look further into the foundations and will be re- 
warded. But those who are not mathematicians need 
not for that reason fall short of full conviction. It is 
unavoidable to speak of the theory, in description or 
exposition, as “ explaining ”’ certain facts of experience. 
But the theory is non-mechanical—in fact, is nowadays 
identical with the quantum theory—and “ explanation” 
by the theory cannot mean explanation in the classical 
sense. Explanation of a fact can mean no more than 
its correlation with and co-ordination among an existing 
