August i8, 192 i] 



NATURE 



7^7 



tion diminishes less rapidly with separation than 

 the repulsion, there is a surplus of attraction which 

 provides a tensile resistance. If the applied 

 force is increased, the resistance will also increase 

 up to a certain value, depending on the rates at 

 which the attraction and repulsion respectively 

 change. Further strain causes failure. On the 

 other hand, if a compressive force is applied the 

 particles are brought together and there is a 

 surplus of repulsion which, like the surplus of 

 attraction, varies with the amount of the strain, 

 but differs in that it may be indefinitely great for 

 very high proximity of the particles. 



As to the rationale of the process little can be 

 said. The dynamic energy of the oscillating par- 

 ticles and the consequent rigidity of the atoms and 

 molecules seem to provide a kinetic basis for the 

 repulsion. As is well known, most solids con- 

 tract when they lose heat, and, since heat is elec- 

 tronic, the fact that most solids increase in 

 cohesion when cooled would be quite consistent 

 with atomic and molecular oscillation or rotation, 

 provided that such motion is the cause of repul- 

 sion. 



Whether the attraction is electrical, chemical, 

 dynamic, or unique is not fully determinate, but 

 since there is a fairly consistent hypothesis in terms 

 of electrical theory, a bias in that direction is 

 natural so long as no practical objections occur. 

 Kelvin's gravitative theory seems to be baseless, 

 for it leads to inconsistent results when the actual 

 spacing of molecules is considered : but there is no 

 intrinsic objection to an hypothesis which wouIH 

 make gravitation the residual of cohesive attrac- 

 tion. The writer has developed an empirical 



formula on these lines which gives a con- 

 tinuous expression for cohesion and gravita- 

 tion. Newton's great discovery was that 

 gravitation varies as the product of the masses 

 concerned divided by the square of the distance 

 between their centres, and the success of this law 

 in explaining the motions of the heavenly bodies 

 proves with overwhelming certitude its accuracy 

 for all distances but the smallest, and jjossibly also 

 the enormously great. When, however, the dis- 

 tance is comparable to the usual distance between 

 the centres of the atoms or molecules in a solid a 

 strong doubt as to the applicability of Newton's 

 law arises, for it would appear that when two 

 molecules are separated to twice their usual dis- 

 tance in a fluid the mutual attraction in the second 

 position falls away much more rapidly than 

 Newton's rule implies, and the attractions are 

 quantitatively enormously greater. We may of 

 course suppose, as did Sutherland, that gravita- 

 tion has nothing to do with cohesion, but this does 

 not satisfy the craving for continuity. 



Here, then, is a field for investigation of the 

 highest practical importance. If cohesion can be 

 properly connected to other physical properties it 

 is conceivable that new compounds of great 

 strength, due to a critical state of cohesion arti- 

 ficially produced, would be found. Chemistry, 

 crystallography, metallurgy, and engineering 

 would all benefit by such an advance in knowledge 

 of the ordinary properties of matter. Somewhat 

 paradoxically it would appear that a complete 

 solution of the macroscopic properties of matter 

 would also solve the question of the inner struc- 

 ture of the molecules and atoms. 



International Conference of Chemistry. 



THE International Conference of Pure and 

 Applied Chemistry held at Brussels at the 

 end of June was nominally the second of these 

 conferences, that at Rome in 1920 being the first; 

 but there were at least two earlier assemblies in 

 London and Paris which led up to the organisa- 

 tion, which seems now to be firmly established. 



More than twenty countries are included in the 

 organisation, Germany, Sweden, and Austria being 

 the principal ones which are not yet represented. 

 A number of well-known chemists took part 

 in the conference : — Profs. Chavanne, Crismer, 

 Swartz, and Timmermans (Belgium), Billmann 

 (Denmark), Conant and Mackall (United States), 

 Moureu, B(^hal, Matignon, and Urbain (France), 

 Pope and Lowry (England), Garelli and Nasini 

 (Italy), Halvorsen (Norway), HoUeman and Kruyt 

 (Holland), Guye and Pictet (Switzerland), and 

 several representatives of industrial chemistry, 

 including M. Kestner, to whose energy and deter- 

 mination the organisation is so much indebted. 



Each of the countries concerned has a council 

 corresponding to the British Federal Council for 

 Pure and Applied Chemistry, and the various 

 national councils appoint members of the Inter- 



NO. 2703, VOL. 107] 



national Council and send in addition delegates 

 to the annual conferences. So far as Great 

 Britain is concerned, the Federal Council has 

 invited its president. Sir William Pope, Prof. 

 Philip, Dr. M. O. Forster, Mr. E. V. Evans, and 

 the two honorary secretaries. Prof. H. E. Arm- 

 strong and Dr. Stephen Miall, to serve on the 

 International Council for the next three years. 



The work of the International Conference is 

 divided among a number of commissions dealing 

 with specific subjects or proposals of an inter- 

 national character. Among these the Commission 

 on Chemical Elements will replace the former 

 Commission on Atomic Weights. It was felt 

 that the exact determination of atomic weights 

 and their publication to several places of decimals 

 has now lost a good deal of its scientific signifi- 

 cance in view of the work of Dr. Aston and others, 

 and that exact atomic weights are now becoming 

 factors of analytical calculation rather than fea- 

 tures of a chemical hypothesis. The isotopes or 

 atomic numbers are taking the premier place, 

 and the atomic weights — often representing merely 

 the average of a mixture of isotopes — will be of 

 practical rather than theoretical interest. The 



