254 



NATURE 



[May 30, 191 8 



included, especially at times of the day when convection 

 currents are not in evidence in the lower atmosphere, 

 otherwise double observations by day and by nif*htwere 

 obtained with different base-lines of approximately half 

 a mile, one mile, and one and a half miles in length. 

 Some hundreds of ascents were observed, of which a 

 fair proportion reached a height between 9 and 11 km., 

 only 30 per cent, failing to reach the 4-km. level. 



The data are admittedly insufficient to determine a 

 diurnal oscillation, but Dr. van Bemmelen is fairly 

 satisfied with the result for the semi-diurnal one. The 

 east and north components. are treated separately, and 

 it is found that the former has a greater amplitude 

 than the latter, and also a better determined phase. 

 Gold's theoretical results for the lower layers are con- 

 firmed {Phtl. Mag., vol. xix.). The phase of the east 

 component diminishes up to 4 km., and probably in- 

 creases above that height, showing a fairly close 

 <inalogy with the vertical oscillations. W. W. B. 



RECONSTRUCTION IN FRANCE. 

 'T*HE issue of the Revue Scientifique for April 13 

 -'• contains evidence that our French neighbours are 

 discussing the problems of reconstruction on much the 

 same lines as we are. In an article on agriculture in 

 19 17, M. Albin Haller, president of the Academic d 'Agri- 

 culture, deals with the present effects of the war on 

 agriculture and the outlook after the war, particularly 

 in regard to the supiply of artificial manures. He 

 points out that war conditions have led to a diversion 

 of the supply of nitrogenous manures to the manu- 

 facture of explosives, and that after the war it vv'ill be 

 necessary to imake up for the lost fertility of the soil 

 by State efforts in the direction of stimulating the 

 home supply of nitrogenous fertilisers from such 

 sources as the by-products of gas- and coke-making, or 

 even from special. plants devoted to nitrogen fixation. 

 In regard to the latter, (he rightly points out .that the 

 feasibility may depend upon the harnessing of the 

 wa:terfalls of the country— a point that we might well' 

 take to heart when we consider the immense possibili- 

 ties of the Highlands of Scotland in this direction. 

 M. Haller also throws out suggestions in regard to 

 the future supply of phosphatic (fertilisers, again touch- 

 ing a problem which is engaging attention here. The 

 fact that the State now controls the production of 

 sulphuric acid, and that, owing to its command over 

 Australian zinc "concentrates," it may be able to market 

 the acid as a waste product, inevitably suggests State 

 enterprise in the future production of fertilisers as an 

 adjunct to its ifood-production .campaign. 



An article in the same issue by M. Brucker, 

 Principal of the Lycee de Cherbourg, entitled 

 ■' L'Education de I'esprit scientifique," may be paral- 

 leled by the Report of the Committee appointed by 

 the Prime Minister to inquire into the position of 

 natural science in the educational system of Great 

 Britain. It is perhaps characteristic of the two 

 nations that, whereas the former is largely de- 

 voted_ to a discussion of the abstract and logical 

 principles of scientific education — ^whether, for example, 

 the methods should be synthetic or analytic — the latter 

 concerns itself largely with the concrete problems of 

 curricula, supply and training of teachers, etc. One 

 rarely reads the writings of an educated Frenchman 

 without having some cause to envy his possession of 

 a language which is such an elegant vehicle for the 

 picturesque, and, at the same time, precise expression 

 of ideas. Such an instance can (be cited in M. 

 Brucker's characterisation of scientific definition as 

 "une luitte oontre le .psittacisme," or, when quoting 

 another writer, he speaks of "battant lapaille desmots 

 pour en faire tomber le grain des choses." May we com- 

 mend the latter operation to our politicians? B. 

 NO. 2535, VOL. lOl] 



I 



RADIATION AND THE ELECTRON.^ 

 II. 

 N spite of the credentials which have just been pre- 

 sented for Einstein's equation, we are confronted 

 with the extraordinary situation that the semi-corpus- 

 cular theory out of which Einstein got his equation 

 seems to be wholly untenable, and has, in fact, been 

 pretty generally abandoned, though Sir J. J. Thomson - 

 and a few others^ seem still to adhere to some form 

 of aether-string theory— that is, to some form of theory 

 in which the energy remains localised in space instead 

 of spreading over the entire wave front. 



Two very potent objections, however, may be urged 

 against all forms of aether-strmg theory, of which Ein- 

 stein's is a particular modification. The first, is that 

 no one has ever yet been able to show that such a 

 theory can predict any one of the facts of interference. 

 The second is that there is direct positive evidence 

 against the view that the aether possesses a fibrous 

 structure. For if a static electrical field has a fibrous 

 structure, .as postulated by any form of jether-string 

 theory, "each unit of positive electricity being the 

 origia, and each unit of negative electricity the termina- 

 tion, of a Faraday tube," ' then the force acting on one 

 single electron between the plates of an air condenser 

 cannot possibly vary continuously with the potential 

 difference between the plates. Now in the oil-drop ex- 

 periments {Phys. Rev., vol. ii.[i9i3], p. 109) we actually 

 study the behaviour in such an electric field of one 

 single, isolated electron, and we find, over the widest 

 limits, exact proportionality between the field strength 

 and the force acting on the electron as measured bv 

 the velocity with which the oil drop to which it is 

 attached is dragged through the air. 



When we maintain the field constant and vary the 

 charge on the drop, the granular structure of "elec- 

 tricity is proved by the discontinuous changes in the 

 velocity, but when we maintain the charge constant 

 and vary the field the lack of discontinuous change in 

 the velocity disproves th^ contention of a fibrous struc- 

 ture in the field, unless the assumption be made that 

 there are an enormous number of aether strings ending 

 in one electron. Such an assumption takes all the 

 virtue out of an aether-string theory. 



Despite, then, the apparently complete success of the 

 Einstein equation, the physical theory of which it was 

 designed to be the symbolic expression is found so un- 

 tenable that Einstein himself, I believe, no longer holds 

 to it, and we are in the position of having built a verv 

 perfect structure and then knocked out entirely the 

 underpinning without causing the building to fall. It 

 stands complete and apparently well tested, but without 

 any visible means of support. These supports must 

 obviously exist, and the most fascinating problem of 

 modern physics is to find them. Experiment has out- 

 run theory, or, better, guided by erroneous theory, it 

 has discovered relationships which seem to be of the 

 greatest interest and importance, but the reasons for 

 them are as yet not at all understood. 



It is possible, however, to go a certain distance to- 

 wards a solution and to indicate some conditions which 

 must be satisfied by the solution when it is found. For 

 the energy hv with which the electron is found by ex- 

 periment to escape from the atom must have come 

 either from the energy stored up inside the atom 

 or else from the light. There is no third possibility. 



1 Address to the Section of Phvsics and Chemistry of the Franklin 

 Institutr, Philadelphia, on January 4, 1917, by Prof. R. A. Millikan, pro- 



•fessor of physics in the University of Chicago. The substance of this lecture 

 has since been incorcorated into a book recently issued by the University of 

 Chicago Pres.s, entitled " The Electron." Continued from p. 237. 



2 Proc. Phy.s. Soc. of ]-ondon, vol. .\xvii. (December 15, 1914), p. 105. 

 •'"Modern Electrical Theory" (Cambridge University Pre.ss, 1913), 



p. 248. 



■* J. J. Thomson, " Electricity and Matter," p. 9. 



