May 6, 1922] 



NATURE 



581 



in the latter case biologists will be compelled, by 

 pressure from outside, especially from the followers 

 of other sciences, to adopt the right methods, what- 

 ever they may be. But I am concerned with mind 

 nid education, and the moment one tries to reach 

 1 )ed-rock in such matters one finds oneself in biological 

 (juicksands. One is told that some characters are 

 innate and some acquired, but not the distinction 

 between the innate and the acquired. It is under- 

 stood that things that are learned are acquired, but 

 apparently no one has tried to ascertain how much 

 is learned or how it is learned. Seemingly, all 

 biologists are agreed that, in themselves, acquired 

 characters are trifling things ; but while Lamarckians 

 think them important through their cumulative 

 effects, neo-Darwinians, conceiving them as transient, 

 think them unworthy of study. Both parties mean 

 one thing when they apply the word " inherit " to 

 " innate " characters, and the exact opposite when 

 they apply it to " acquirements." 



Man is the educable animal, say some biologists. 

 He is not educable, say (in effect) others who declare 

 that in his mental make-up nature is four, perhaps 

 nine, times more potent than nurture. One admires 

 the precision of statement, but wonders what is 

 meant. As I understand it, man's nature is such that 

 he is particularly responsive to the nurture of mental 

 use. It is as if a physicist had stated that the steam 

 is four, perhaps nine, times more potent than the 

 engine. And so on. Meanwhile, prejudice controls 

 education and society flows towards the cataracts. 

 I may be very ignorant as to facts and mistaken 

 in my opinions, but in that case my demolition should 

 be a holiday task to the trained and learned intellect. 

 Failing demolition, I cannot help believing that 

 biologists do not realise how very great their science 

 is, or might be, and how vitally and immediately 

 important their labours are, or should be. In- 

 cidentally, I have sought in these letters of mine to 

 indicate the high importance, as it appears to me, 

 of classifying characters, not as innate and acquired, 

 but, as physiologists do, according to the stimuli 

 which cause them to develop. So far as I am able 

 to judge, unless scientific men ascertain precisely 

 how mental characters are developed, and then 

 vigorously apply their knowledge for the betterment 

 of education, modern society will soon be on the 

 rocks. G. Archdall Reid. 



9 Victoria Road South, Southsea, Hants. 



I the type referred to by Prof. Robinson. It may 

 be possible to determine to what extent, if at all. 

 this stability involves a modification of the norrnal 

 benzenoid properties associated with two benzene 

 nuclei. Differences between diphenyl itself and 

 benzene in respect of their molecular refraction, and 

 behaviour on catalytic reduction and towards ozone, 

 are already on record, so that it will also be pertinent 

 to inquire whether the fixity of configuration is a 

 general property of diphenyl derivatives, or is 

 dependent on the nature of the substituents present, 

 and connected, for example, with the observations 

 of Baly and Collie (Trans. Chem. Soc, 1905, 1339) 

 on the modification of the ultra-violet absorption of 

 benzene by the introduction of a nitro group. 



In any case, our result would appear to supply 

 the first direct experimental proof that other con- 

 figurations of the separate benzene molecule may 

 exist than the plane (Kekul6) type. For the great 

 majority of chemists, who also recognise the merits 

 of the Kekul6 formula, or some modification of it, 

 this will involve the acceptance of some dynamic 

 conception, such as, for example, has been advocated 

 by CoUie and by Bloch. It will be noted that one 

 phase of Bloch's formula corresponds closely to 

 that deduced by Sir William Bragg from his 

 observations on the diamond and on naphthalene and 

 its, derivatives. 



it should perhaps be pointed out that the above 

 suggestions depend for their validity on the assump- 

 tion that the relationship between the isomerides is 

 stereochemical in the ordinary sense. There is always a 

 possibility, which, however, will perhaps be generally 

 considered remote, that the difference may be rather 

 one of structure, in that the two compounds contain, 

 for example, different types of nuclei. ' 



J. Kenner. 



The University, Sheffield, April 21, 1922. 



Configurations of Molecules of Benzenoid Substances. 



Prof. Robinson's remarks (Nature, April 15, 

 p. 476) on Sir William Bragg's representation of the 

 naphthalene molecule, as it occurs in crystals, lead 

 me to invite attention to results obtained recently 

 by Mr. G. H. Christie and myself. In a paper which 

 will be published in the forthcoming number of the 

 Journal of the Chemical Society, the resolution of 

 trans-6 : 6'-dinitro-diphenic acid into optically active 

 components is described. This, with the fact that 

 an apparently homogeneous brucine salt has been 

 obtained from the cis-ioTm of the acid, indicates that 

 in the separate molecules (as distinguished from their 

 crystalline aggregates, to which Sir William Bragg's 

 results apply) of these compounds the two benzene 

 nuclei are not coplanar. 



If this be so, it follows that the direction of the 

 valency of each of the carbon atoms through which 

 these nuclei are united is not, as represented in the 

 usual formulae for benzene, exerted in the plane of 

 the benzene ring, and -further, that this condition is 

 a stable one rather than a phase of an oscillation of 



NO. 2740, VOL. 109] 



The Speed of Light. 



In a discussion in Nature last year (March 10, 

 vol. 107, p. 42) Majorana's experiment was cited as 

 direct proof that the velocity of light is independent 

 of the motion of the source. In reality, however, 

 there is a disadvantage in his method which seems 

 to the writer very greatly to lessen the value of his 

 results. 



Majorana measured the wave-length of the green 

 light from a moving mercury-vapour tube by means 

 of a Michelson interferometer, and detected the change 

 of wave-length that is required by the usual Doppler 

 theory {Phil. Mag., 37, p. 145, 1919). Now it is 

 easily seen that the frequency of the waves arriving 

 at the receiving apparatus will undergo the usual 

 Doppler change whether the speed of propagation is 

 altered (moderately) or not, and speed equals wave- 

 length times frequency, hence Majorana concludes 

 that the speed of the light from his tube was the 

 same when the tube was moving as when it was at 

 rest. But obviously he measured the wave-length 

 only after the light had suffered one or two reflections 

 or transmissions in stationary apparatus, and its 

 velocity might easily have been altered by these 

 processes. Any conclusion from his results must 

 therefore rest, at best, upon very indirect reasoning. 



We may freely admit that a satisfactory emission 

 theory consistent with all the facts that are known to- 

 day, including Majorana's result, would be difficult to 

 construct. Yet it does seem regrettable that we have 

 still no simple direct proof of the second postulate 

 of Relativity. 



U 2 



