September 9, 1922] 



NA TURE 



34i 



Letters to the Editor. 



The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of rejected manuscripts intended for 

 this or any other part of NATURE. No notice is 

 taken of anonymous communications.'] 



The British Association. 



The Association is to consider whether it will once 

 more adventure into the outer regions of the Empire. 

 That such transgress is desirable I am satisfied and 

 so stated most definitely in the lecture I gave in 1915, 

 at the Royal Institution, on our Australian excursion. 

 In the interest of the younger scientific generation 

 and of our Empire, it is of the utmost importance 

 that we should roam over the world and discover its 

 amenities — but the effort must be wholehearted, 

 whenever it be made. The one failure of our Australian 

 expedition was the insufficient support of the younger 

 men. 



It is a question whether, at the present time, when 

 the cost of travel is so high, it will be desirable to 

 attempt a new expedition — the chance that it will 

 be well supported by the young men is not great. 

 The Society of Chemical Industry could carry only 

 a very small party last year to Canada. Therefore, 

 the choice of a region that shall not be too distant is 

 desirable, if the decision be to travel. 



Properly speaking, the Association should go 

 further westward, to British Columbia, north of the 

 C.P.R., to visualise its potentialities and gain some 

 idea of its conditions. To recommence the cycle at 

 a middle point such as Toronto seems undesirable, 

 at present. Montreal is the natural and would be 

 the proper point of redeparture and discovery. It 

 has also the advantage that it is the centre of the only 

 region on the American continent where freedom still 

 prevails and men are thought to be capable of taking 

 care of themselves. It is the duty of science to 

 protest and erect some barrier against the advancing 

 wave of spurious puritanism which so affects Americans 

 and now so threatens the freedom of mankind. The 

 recent all but successful attempt to ban Darwinism 

 in every shape and form is sufficient proof of what 

 may happen. Henry E. Armstrong. 



Bohr and Langmuir Atoms. 



Chemists feel a difficulty in explaining molecular 

 combination in terms of electrical attraction between 

 the apparently revolving electrons which seem to 

 compose the peripheral parts of an atom ; and they 

 naturally prefer a more static arrangement. Indeed, 

 it is not easy to explain the stability of molecules 

 in terms of any kind of purely electrical attraction 

 between the atoms composing them : and yet, ever 

 since Faraday, there has been an instinctive feeling 

 that electrical attraction and chemical affinity are 

 one and the same. 



The facts of spectroscopy seem to insist on a system 

 of revolving electric charges, while the facts of 

 chemical combination seem to demand forces which 

 can be treated statically ; so it has been suggested 

 that internal electrons are responsible for the radia- 

 tion, while external electrons control the chemical 

 forces. But the stability of chemical compounds 

 can scarcely depend on loosely held external electrons, 

 which, moreover, ought to be revolving just as much 

 though not so fast as the inner ones. 



May not a reconciliation be found by abandoning 

 the idea of electrical attraction between atoms as the 



NO. 2758, VOL. I IO] 



major chemical force, and substituting for it the 

 interlacement of the magnetic fields which inevitably 

 accompany rapidly revolving electric charges. The 

 orbital motion of the electrons responsible for chemical 

 affinity, so far from constituting a difficulty, gives us 

 a clue ; for in every magnet electrons are rapidly 

 revolving, and yet magnetic force is static. The 

 clinging together of nails or needles near a magnet 

 is all due to revolving electrons. Working with 

 magnetised steel spheres, tetrahedra, and other 

 shapes, some one with the ingenuity of Dr. Langmuir 

 or Prof. Bragg might succeed in building up structures 

 or models of adequate chemical significance. 



The difficulty about substituting a magnetic field 

 for an electric' one, as accounting for the facts of 

 chemical affinity, is no doubt the double polarity. 

 But, on the other hand, this inevitable feature gives 

 greater scope as well as greater complexity, and may 

 ultimately be found to be an advantage ; in fact, I 

 am beginning to think that the constitution of bodies 

 cannot be explained without it. The phenomena 

 which long ago suggested "normal- and contra- 

 valence " would fall into line. The stability of 

 chemical combination would be all that could be 

 desired, and the electrons in each atom would be 

 peacefully engaged in giving their spectroscopic 

 evidence (so well interpreted by the genius of Prof. 

 Bohr), unharassed in their movements and perturba- 

 tions by having to associate themselves with any 

 electric field other than that of their own nucleus. 

 Their magnetic linkages would be a sort of uncon- 

 scious extra. 



The undoubted phenomenon of ionisation would 

 have to be developed independently, along with other 

 known facts about gross positive and negative electric 

 charges, but in the formation of stable chemical 

 molecules we should not have to appeal to ionic charge. 

 Moreover, certain molecular groupings, held together 

 by magnetic forces, might be found readily susceptible 

 to ionisation, especially when subject to bombard- 

 ment, or when packed close together in a liquid. 



I do not suppose that magnetic attraction as the 

 equivalent of chemical affinity is any new idea, but 

 I suggest that it has been inadequately developed, 

 and that it seems capable of effecting a reconciliation 

 between the extraordinarily ingenious schemes — 

 apparently opposed, and yet both containing elements 

 of truth — of which the names at the head of this 

 letter may be regarded as principal types. 



Oliver Lodge. 



The Acoustics of Enclosed Spaces. 



Since writing the letter published in Nature of 

 August 19, p. 247, my attention has been directed to 

 a paper on " Sound Proof Partitions " by Prof. R. F. 

 Watson (University of Illinois Bulletin for March 

 1922). The paper contains a valuable experimental 

 investigation on one aspect of the subject, but much 

 remains to be done. 



I take this opportunity of correcting an error which 

 seriously affects the numerical results I gave for the 

 sound transmitted through walls. In applying the 

 optical equations, I forgot for the moment that the 

 intensity of reflection in the case of sound does not 

 only depend on the refractive index but also on the 

 relative densities of the two bodies concerned. Even 

 if the refractive indices were equal, so that the sound 

 would proceed in the same direction, there would 

 still be a powerful reflection if the densities were very 

 unequal. In the equation I gave, 1 - 1±- should be 

 replaced by a-ix-a- 1 , where a. is the ratio of the 

 densities. "When sound passes from air to a solid 

 body the second term is in general negligible, and 



