418 Dr. S. H. 0. Briggs : The Elements 



the modulus equals — 2a. This may be obtained by intro- 

 ducing increments in the linear dimensions in the general 

 expression for the modulus. On the other hand, it may be 

 shown in a similar manner that the part contributed by the 

 thermal expansion of a tuning-fork to the temperature 



coefficient of its period equals -. Therefore denoting the 



temperature coefficients of E and P due, purely, to changes 

 in the elastic properties of the substance by e' and $', respec- 

 tively, we have 



€ = e'-2u (19) 



and M' + f- ...... (20) 



Substituting these in (10), we obtain 



e'=-2<9' (2.1) 



LI. The Elements regarded as Compounds of the First 

 Order. By S. H. 0. Briggs, D'.Sc* 



THE object of this communication is to draw attention to 

 a striking parallelism between the properties of the 

 chemical elements on the one hand, and those of the simpler 

 compounds on the other. The subject is treated from the 

 point of view of the theory of duplex affinity developed by 

 the author in previous papers (Trans. Chem. Soc. xciii. p. 1561 

 (1908); cxi. p. 253 (1917) ; cxv. p. 278 (1919)), the atoms 

 being regarded as compounds of the atomic kernels and 

 electrons, built up in accordance with Langmuir's theory of 

 atomic structure (J. Ainer. Chem. Soc. xli. pp. 868, 1543 

 (1919) ; xlii. p. 271 (1920) ; see also G. N. Lewis, ibid. 

 xxxviii. p. 762 (1916)). Lewis uses the word kernel to 

 describe what remains of the atom after all the electrons in 

 the outside shell (valency electrons) have been removed. 



The kernels are denoted in this paper by the symbol of 

 the element with a small k written above, as K. k and Na*, the 

 potassium and sodium kernels. The electron is represented 

 byE. 



Polar and non-polar elements. 



For the sake of simplicity it is assumed that the kernels 

 are spheres, in the same way, and with the same justification, 

 that the atoms were supposed to be spheres in a former 



* Communicated by the Author. 



