June 3, 1922J 



NATURE 



Jig 



but, in view of the fact that radiation by the atom is 

 attributed to the movement of electrons from one orbit 

 to another, the prospect of realising two different stable 

 configurations of the orbits appears somewhat remote. 

 Another possibility, that atoms may exist of equal 

 atomic weight as well as of equal atomic number, has 

 been discussed in connection with certain members of 

 the radium and actinium series or radio-elements. The 

 supposed necessity for recognising this subtle type of 

 distinction between atoms is based on the assumption 

 that radium and actinium are derived from a common 

 parent and that all the members of both series of radio- 

 elements must therefore have atomic weights of the 

 type (238 - 4«). If, however, radium and actinium are 

 derived from isotopic forms of uranium, the two series 

 of radio-elements may well prove to differ in atomic 

 weight, e.g. by one unit. The discussion on Aston's 

 paper dealt largely with the question of how an " ele- 

 ment " should be defined, in view of the discovery of 

 isotopes not only amongst radio-elements but also 

 amongst the common elements. Aston appeared to 

 voice the feeling amongst physicists by suggesting that 

 each atomic number should represent one element ; 

 but he was opposed by a number of chemists, who 

 argued that the word " element " carried with it an 

 idea of homogeneity which could not be reconciled with 

 the proposal to describe as an element a mixture of 

 isotopes, the separation of which might at any time 

 become a practical possibility. The paper on the 

 separation of isotopes, presented by Perrin and Urbain, 

 was to have been prepared by the late Prof. Guye. It 

 certainly served to emphasise the extreme difficulty of 

 the separation, since nearly all the methods derived 

 from analogy with rare earths or isomeric hydrocarbons 

 have been shown, both by theory and by experiment, 

 to be impracticable. 



Bragg's demonstration of recent results obtained by 

 the X-ray analysis of crystals was greatly aided by 

 models, which could be not only viewed at close 

 quarters, but handled and studied during the whole 

 period of the conference. Some discussion arose in 

 connection with his demonstration of the relationship 

 between the crystal structure of diamond and of 

 graphite, and of the two kinds of relationship between 

 carbon atoms which are shown by the model of graphite. 

 Two different kinds of linkage were also shown between 

 atoms of bismuth, corresponding perhaps to co-valence 

 and electro- valence respectively. The principal sub- 

 ject of discussion arose, however, from the application 



of X-ray analysis to organic compounds and a be- 

 wildering array of chemical problems was suggested, 

 in connection with which X-ray analysis might lead 

 to useful results. A modification of Barlow and Pope's 

 theory of crystal structure, in which a quadrivalent 

 atom is represented by an aggregate of four unit 

 spheres, was described, and sliown to present many 

 points of close agreement with the crystalline structure 

 actually recorded in organic compounds. 



The discussion on the electronic theory of valency 

 which followed Mauguin's paper included perhaps a 

 larger proportion of adverse criticism than is usually 

 accorded to it. In particular, the lack of any adequate 

 explanation of variable valency, and the indeterminate 

 character of the valency equations (which do not admit 

 of a unique mathematical solution) were the subjects 

 of much comment. 



The discussion on optical activity dealt mainly with 

 the usefulness or otherwise of retaining the idea of the 

 asymmetric carbon atom. It was agreed that the 

 asymmetry of the molecule was the only thing that 

 mattered ; but expression was given to the view that 

 the term was of value as enabling the organic chemist 

 to recognise at once the existence of many cases of 

 molecular asymmetry, although this might still be 

 looked for in many cases where no asymmetric atom 

 was present. In the discussion on rotatory dispersion 

 the idea was expressed that liquid media which gave 

 rise to complex dispersion-curves might be suspected 

 of containing more than one type of optically-active 

 molecule ; in the case of coloured compounds, however, 

 a looped curve might result from the presence of an 

 absorption band in the region under investigation. 



The discussion on chemical mobility was for the most 

 part focussed on the radiation theory of chemical action. 

 The lack of agreement between the predictions of the 

 theory, and the results obtained in seeking to verify 

 it, was emphasised. Thus, the observed temperature 

 coefficient of the thermal dissociation of phosphine 

 leads to the conclusion that an absorption band should 

 appear in the violet region of the spectrum. No such 

 band is found, and the theory has therefore been 

 modified in a way which suggests that the active 

 radiations may be found at lower frequencies, e.g. in 

 the infra-red region of the spectrum. Actually, how- 

 ever, the change is very sensitive to ultra-violet radia- 

 tions, and a further modification of the theory would 

 be needed to account for this persistent deviation from 

 the experimental facts. 



Universal Wireless Telephony. 



IN view of the . great technical progress that has 

 been made during the last few years in the 

 development of the wireless telephone, and the atten- 

 tion that has been given by the Postmaster-General 

 to the framing of regulations for its orderly use in 

 this country, a considerable popularisation of wireless 

 telephony appears imminent. It is therefore of some 

 interest to examine briefly the facilities as well as 

 the limitations which exist regarding its use. It is 

 obvious that anything like secrecy in conversation 

 over the radio-telephone, as it is now often called, is 

 out of the question, as any one in possession of a half- 



NO. 2744, VOL. 109] 



guinea licence and a receiving set, which can be tuned 

 to the wave-length employed, can " listen in " and 

 pick up the message irrespective of the station ior 

 which it was primarily intended. On account of the 

 publicity which thus attends the utterances of the 

 wireless telephone, its field, except in such special 

 cases as aeroplane work, is practically limited to the 

 dissemination of public information, news, music, 

 and other entertainment items, or as it is now com- 

 monly called, " broadcasting." Unless, however, these 

 broadcasting stations are rigorously controlled, they 

 will not only defeat their own ends by drowning each 



