66 Major W. T. David on the Calculation of 



symmetry) was uniquely privileged. But from the present, 

 more general point of view there is certainly no reason for 

 rejecting a meridian plane as the reference plane (i = 0), and 

 this, i. e. any such reference plane, will precisely give, in 

 addition to (28*1) the new coefficient (28*1 / ) and thus also 

 new lines or components. 



Still, the asymmetric nucleus will be richer in possible 

 lines or components. Which of these are to be rejected, 

 can be decided only on the ground of spectroscopic experience. 

 One might put forward, for instance, as a restricting cri- 

 terion that out of the three 7-values (30*2), that only is to 

 be retained to which, cceteris paribus, corresponds the greatest 

 W s , or perhaps the smallest W s , or what not. But all such 

 guesswork, unsupported by observation, would be pretty 

 useless. 



The chief purpose of the present paper has been to show 

 the numerous and broad possibilities opened up by a non- 

 spherical nucleus both with regard to the fine structure of 

 lines or groups and to the very type of the spectrum series. 

 All numerical applications of the general formulae and their 

 discussion in connexion with experimental spectroscopic 

 knowledge are necessarily postponed to a later opportunity. 



Research Dept., Adam Hilo-er. 

 London, October 18, 1919. 



VI. The Calculation of Radiation emitted in Gaseous Explosions 

 from the Pressure-Time Curves. By Major W. T. David, 

 M.A., M.Sc* 



Introduction. 



1. TN this paper an attempt is made to build up formulae 

 JL by means of which the radiation emitted in explosions 

 of inflammable mixtures of coal-gas and air may be calcu- 

 lated from the pressure-time curves. A large number of 

 photographic films on which were traced curves of pressure 

 and of radiation emitted f have been examined, and it lias 

 been found possible to establish some simple equations which 

 would seem to apply within fairly wide limits of mixture 

 strength, density, and volume. 



* Communicated by the Author. 



f Curves taken from a considerable number of these films have 

 previously been published in the Phil. Trans. (A. vol. ccxi. pp. 375-410). 

 Reference should be made to this paper for full details of the experi- 

 mental methods employed. 



