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PRESIDENT’S ADDRESS. 7 
must occur in bodies moving at speeds nearly comparable with that of 
light. It turns out in fact that both Shape and Mass are functions 
of Velocity. As the speed increases the mass increases and the shape 
is distorted, though under ordinary conditions only to an infinitesimal 
extent. 
So far I agree; I agree with the statement of fact; but I do not 
consider it so revolutionary as to overturn Newtonian mechanics. 
After all, a variation of Mass is familiar enough, and it would be a great 
mistake to say that Newton’s second law breaks down merely because 
Mass is not constant. A raindrop is an example of variable mass; or 
the earth may be, by reason of meteoric dust; or the sun, by reason of 
radio-activity; or a locomotive, by reason of the emission of steam. 
In fact, variable masses are the commonest, for friction may abrade 
any moving body to a microscopic extent. 
That Mass is constant is only an approximation. That Mass is 
equal to ratio of Force and Acceleration is a definition, and can be 
absolutely accurate. It holds perfectly even for an electron with a 
speed near that of light ; and it is by means of Newton’s second law that 
the variation of Mass with Velocity has been experimentally observed 
and compared with theory. 
I urge that we remain with, or go back to, Newton. I see no 
reason against retaining all Newton’s laws, discarding nothing, but 
supplementing them in the light of further knowledge. 
Even the laws of Geometry have been overhauled, and Euclidean 
Geometry is seen to be but a special case of more fundamental generali- 
sations. How far they apply to existing space, and how far Time 
is a reality or an illusion, and whether it can in any sense depend on 
the motion or the position of an observer: all these things in some form 
or other are discussed. 
The Conservation of Matter also, that main-mast of nineteenth 
century chemistry, and the existence of the Ether of Space, that sheet- 
anchor of nineteenth century physics,—do they not sometimes seem 
to be going by the board? 
Professor Schuster, in his American lectures, commented on the 
modern receptive attitude as follows :— 
‘The state of plasticity and flux—a healthy state, in my 
opinion,—in which scientific thought of the present day adapts 
itself to almost any novelty, is illustrated by the complacency with 
which the most cherished tenets of our fathers are being aban- 
doned. Though it was never an article of orthodox faith that 
chemical elements were immutable and would not some day be 
resolved into simpler constituents, yet the conservation of mass 
seemed to lie at the very foundation of creation. But now-a-days 
