eS rr SOr—”—” 
PRESIDENT’S ADDRESS. 15 
technicality, is expected on Friday in Section A. We welcome Pro- 
fessor Lorentz, Dr. Arrhenius, Professor Langevin, Professor Prings- 
heim, and others, some of whom have been specially invited to England 
because of the important contributions which they have made to the 
subject-matter of this discussion. 
Why is so much importance attached to Radiation? Because it is 
the best-known and longest-studied link between matter and ether, and 
the only property we are acquainted with that affects the unmodified 
great mass of ether alone. Electricity and magnetism are associated 
with the modifications or singularities called electrons: most phenomena 
are connected still more directly with matter. Radiation, however, 
though excited by an accelerated electron, is subsequently let loose in 
the ether of space, and travels as a definite thing at a measurable and 
constant pace—a pace independent of everything so long as the ether 
is free, unmodified and unloaded by matter. Hence radiation has much 
to teach us, and we have much to learn concerning its nature. 
How far can the analogy of granular, corpuscular, countable, atomic, 
or discontinuous things be pressed? There are those who think it can 
be pressed very far. But to avoid misunderstanding let me state, for 
what it may be worth, that I myself am an upholder of ultimate 
Continuity, and a fervent believer in the Ether of Space. 
We have already learnt something about the ether; and although 
there may be almost as many varieties of opinion as there are people 
qualified to form one, in my view we have learnt as follows: F 
The Ether is the universal connecting medium which binds the 
universe together, and makes it a coherent whole instead of a chaotic 
collection of independent isolated fragments. It is the vehicle of 
transmission of all manner of force, from gravitation down to cohesion 
and chemical affinity ; it is therefore the storehouse of potential energy. 
_ Matter moves, but Ether is strained. 
What we call elasticity of matter is only the result of an alteration 
of configuration due to movement and readjustment of particles, but 
all the strain and stress are in the ether. The ether itself does not 
move, that is to say it does not move in the sense of locomotion, 
though it is probably in a violent state of rotational or turbulent 
motion in its smallest parts; and to that motion its exceeding rigidity 
is due. 
As to its density, it must be far greater than that of any form of 
matter, millions of times denser than lead or platinum. Yet matter 
moves through it with perfect freedom, without any friction or 
viscosity. There is nothing paradoxical in this: viscosity is not a 
function of density; the two are not necessarily connected. When a 
solid moves through an alien fluid it is true that it acquires a spurious 
or apparent extra inertia from the fluid it displaces; but, in the case 
