1892.] Prof. 0. Lodge on the Motion of the EtJier, dc. 565 



WEEKLY EVENING MEETING, * 



Friday, April 1, 1892. 



William Huggins, Esq. D.C.L. LL.D. Ph.D. F.R.S. Vice-President, 



in the Chair, 



Professor Oliver Lodge, D.Sc. LL.D. F.E.S. F.R.A.S. 



The Motion of the Ether near the Earth. 



Everybody knows that to shoot a bird on the wing you must aim in 

 front of it. Every one will readily admit that to hit a squatting rabbit 

 from a moving train you must aim behind it. 



These are examples of what may be called " aberration " from the 

 sender's point of view, from the point of view of the source. And 

 the aberration, or needful divergence between the point aimed at and 

 the thing hit has opposite sign in the two cases — the case when 

 receiver is moving, and the case when source is moving. Hence, if 

 both be moving, it is possible for the two aberrations to neutralise each 

 other. So to hit a rabbit running alongside the train you must aim 

 straight at it. 



If there were no air that is all simple enough. But every rifle- 

 man knows to his cost that though he fixes both himself and his target 

 tightly to the ground, so as to destroy all aberration proper, yet a 

 current of air is very competent to introduce a kind of spurious aber- 

 ration of its own, which may be called windage ; and that he must 

 not aim at the target if he wants to hit it, but must aim a little in the 

 eye of the wind. 



So much from the shooter's point of view. Now attend to the 

 point of view of the target. 



Consider it made of soft enough material to be completely pene- 

 trated by the bullet, leaving a longish hole wherever struck. A 

 person behind the target, whom we may call a marker, by applying 

 his eye to the hole immediately after the hit, may be able to look 

 through it at the shooter, and thereby to spot the successful man. I 

 know that this is not precisely the function of an ordinary marker, 

 but it is more complete than his ordinary function. All he does 

 usually is to signal an impersonal hit ; some one else has to record the 

 identity of the shooter. I am rather assuming a volley of shots, and 

 that the marker has to allocate the hits to their respective sources by 

 means of the holes made in the target. 



Well, will he do it correctly ? assuming, of course, that he can do 

 so if everything is stationary, and ignoring all curvature of path, 



