Astronomy and High-speed Inertia. 93 



Third Law meets with some exception. It is. therefore, not 

 unnatural to associate a specific semi-material inertia with 

 the travelling aetherial disturbance which occurs in light. 



The nature of the disturbance is presumably quite different 

 from that accompanying high-speed locomotion of matter : 

 there was nothing likely to simulate general material pro- 

 perties about that. So we are at liberty to ask, concerning 

 the special kind of setherial inertia associated with light-pro- 

 pagation, — Is this momentum-inertia likely to be subject to 

 gravity? In other words, how far does the temporary or 

 travelling aether disturbance in a wave-front correspond to 

 the permanent aether disturbance constituting an electron, 

 which is so interlocked as not to need any locomotion for its 

 existence ? Is it a sort of temporary matter, not permanently 

 constituted, but possessing material properties while it lasts? 

 Experiment must answer the question. An affirmative 

 answer would be of the greatest interest. 



If it be assumed, as probable or possible, that gravitation 

 is one of the properties of this imitation or temporary matter, 

 though its gravitation constant may be q times the ordinary 7 

 [q being either greater or less than 1), the problem of deter- 

 mining the gravitative deflexion of a ray becomes the easy 

 one of reckoning the angle between the asymptotes of a small 

 comet flying in hyperbolic orbit near the sun with immense 

 velocity c. The angle is 



*- 2 !f CD 



where r is its nearest approach to the central body of mass M. 

 This expression for the deflexion 8 agrees with Einstein's 

 predicted value if q is taken as 2 ; though the only reason 

 I can see for that at present is the very speculative one that 

 its gravitational entanglement may depend on the maximum 

 amplitude squared, while its inertia depends on the mean. 



The observational determination of this quantity q is 

 clearly an important one. It may be anything from 2 to 0, 

 though to me the value 1 seems more probable than anything 

 except 0. 



Taking q as 1 for arithmetical purposes, and writing 7M 

 as gR 2 , the value of the deflexion for grazing incidence is 



but V (<?R) is the velocity in a grazing circular orbit, which 

 for the earth is 5 miles a second and for the sun 50 times as 



