1919] on Ether and Matter 475 



gravitation still have many secrets. The interactions between ether 

 and matter are as yet barely understood. AVe know that the energy 

 of an electric current is really in the ether, i.e. in the magnetic field 

 surrounding the current ; but we must admit that the electromagnetic 

 explanation of inertia is no ultimate explanation — it is but relegating 

 the property to some fundamental property of the ether ; of which 

 substance presumably matter itself may in some way be composed. 



Evidence suggests that the ether is an excessively dense substance, 

 and that it circulates slowly along lines of magnetic force.* But 

 though so dense we have no means of apprehending it directly. 

 Matter, though so comparatively filmy and fragmentary, yet looms 

 large in our estimation because of our material sense organs ; its 

 properties force themselves on our attention because in fact our bodies 

 are composed of matter. But underneath and behind all the known 

 properties of matter lie the unknown properties of the ether of space ; 

 and if we are to create a true philosophy we must attend continually 

 to Ether as well as to Matter in the physical universe. The 

 ether makes no appeal to our senses, but it is none the less real for 

 that. Sensation is no test of reality : many of the most important 

 things are in the insensible universe ; and he is the wisest man who 

 shuts the door on no opportunity for investigation, but keeps his 

 mind open, and is ready to explore every avenue towards truth. 



[0. J. L.] 



APPENDIX I. 



Effect on Electronic Orbits of Sudden Nuclear Changes. 



Continuing the subject of the footnote on page 473, and taking the case 

 of an atom degrading by radioactivity, though an inverse process of ascension 

 by building up liqjht atoms into heavy ones can be equally dealt with if that 

 process ever now occurs : let us assume that a nucleus expels first a negative 

 unit and then a positive unit. At the first emission the nucleus, with N 



N 4- 1 

 unbalanced positive charges^ suddenly gains force in the ratio h = — ^^— . 



N 

 The result on its family of revolving electrons is to make every circular 

 orbit elliptical. With the usual Tait and Steele notation, initially R Y- = fx. 

 When the change occurs the semi-major axis of the new orbit is given by 



kV kl 



hence 



2 _ V- 1 U 1\ 



a = ^t 1 R, and e = ^^— . 



N +2 ' N + 1 



* This view of the energy of a magnetic field, that it is direct kinetic energy 

 of the ether moving longitudinally, suggests a possible (or nearly impossible) 

 experimental means of determining the real density of the ether of space— a 

 subject on which I have much more to sav. See probably Phil. Mag. for May, 

 1919. 



