190 Prof. W. M. Thornton on the Limits of 



something which is not matter, and which does not share 

 in the rotation of the condenser, and this something must be 

 the stationary aether of Lorentz. 



This phenomenon seems therefore to lend definite support 

 to the existence of an electromagnetic aether. It is, perhaps, 

 the only low-frequency phenomenon which cannot easily be 

 described in terms of " action at a distance " between 

 electrons and atoms. It seems, for this reason, to have some 

 importance as a stumbling-block in the way of those nltra- 

 relativitists who would abandon the conception of an aether 

 altogether. 



Summary. 



An experiment is described showing that a cylindrical 

 condenser rotating inside a magnetized coaxial solenoid 

 becomes charged as required by the theory of Lorentz. 

 Rotation of the solenoid has no effect (Barnett). 



The disproof of the moving-line theory is thus completed ; 

 electromagnetic induction depends in part upon absolute 

 rotation in the mechanical sense. Analysis in terms of 

 electrons seems to make necessary the existence of a 

 stationary aether in order to explain the observed effect ; so 

 that the phenomenon seems to present difficulties for those 

 relativitists who reject the aether. 



It is a pleasure to acknowledge obligations to Mr. 

 Christian Dane, mechanician, whose share in the con- 

 struction of the apparatus left nothing to be desired ; and 

 to Professor Henry A. Erikson for his kindly interest and 

 advice during the progress of the work. 



University of Minnesota, 

 August, 1916. 



XIV. The Limits of Inflammability of Gaseous Mixtures. By 

 W. M. Thornton, JD.Sc, D.Eng., Professor of Electrical 

 Engineering in Armstrong College, Newcastle-upon-Tyne* '. 



1. FY1HE ignition of an inflammable gas mixed with air 

 J_ depends in a variety of ways upon the proportion 

 of oxygen present. With impulsive sparks or condenser- 

 discharge the ignition passes through critical stages when 

 the ratios of the number of oxygen atoms to one molecule of 



* Communicated by the Author. 



