454 Sir Oliver J. Lodge [Feb. 28, 



WEEKLY EVENING MEETING, 



Friday, February 28, 1919. 



The Right Hon. Lord Wrenbury, P.O. M.A., 

 Vice-President, in the Chair. 



Sir Oliver J. Lodge, D.Sc. LL.D. F.R.S. M.R.I. 



Ether and Matter: Being Remarks on Inertia, and on 

 Radiation, and on the possible Structure of Atoms. 



[Amplified from the Lecture.] 

 Part I. — Inertia. 



We are each of us flying through space at nineteen miles a second, 

 probably much more. Nothing is propelling us; we continue to 

 move by our own inertia, simply because there is nothing to stop us. 

 Motion is a fundamental property of matter. No piece of matter is 

 at rest in the ether, the chances are infinite against any piece having 

 the particular velocity zero ; every bit is moving steadily at some 

 given speed, unless acted on by unbalanced force. Then it is 

 accelerated — changed either in speed or direction, or both. 



As a matter of fact we, like other bodies on the earth, are acted 

 on by two slight unbalanced forces — one which makes us revolve 

 round the earth once a day, like a satellite, the other which makes us 

 revolve round the sun once a year, like a planet or asteroid. Our 

 annual revolution is not because we are attached to the earth ; we are 

 not attached, but revolve as independent bodies, and would revolve 

 in just the same time and way if the earih w^ere suddenly obliterated : 

 only then we should find the diurnal revolution transmuted into a 

 twenty-four hour Hptation round our own centres of gravity, and the 

 excentricity of our annual orbit very slightly changed. In any 

 case there is no propelling force, only a residual radial force producing 

 curvature of path. 



A railway train, or a ship moving steadily, is likewise subject to 

 no resultant force. Propulsion and resistance balance. The whole 

 power of an engine, after the start, is spent in overcoming friction. 

 The motion continues solely by inertia. Any steadily moving body 

 is an example of the first law of motion. You need not try to think 

 of a body under no force at all ; you cannot think of such a body on 

 the earth, but you can think of one under no resultant force, i.e. 

 under balanced forces. Such a body moves by reason of its inertia 

 alone. It is in equilibrium : it is not at rest. 



