exii Proceedings of the Asiatic Society of Bengal. [N.S., XV. 
matter where the anode is placed, and are deflected by a magnet. 
When these are reflected by an aluminum shield, the resulting 
change of momentum yields the ethereal pulse which is held to 
be propagated as X-rays. It is believed that such a discharge 
tube contains electrons, positive particles, and neutral particles, 
existing in varying proportions under varying conditions of 
pressure and electric intensity, and as such has supplied a fruit- 
ful field of inquiry as to their properties. 
ven more remarkable than this is the behaviour of radio- 
active substances. It has now been established beyond mess 
that they spontaneously suffer disintegration, giving off t 
so-called a-rays which are charged helium atoms carrying iis 
units of ocmive charge, B-rays which are electrons possessing 
much greater velocities than the cathode rays generally and 
y-rays which are of the nature of the X-rays. 
We have thus in solids, liquids and gases, which may be 
taken to be different types of singularities of the electro-mag- 
netic field, agglomerations of less complex structure, the pro- 
perties of which are intimately connected with those of the 
electro-magnetic field which modern Physics is attempting to 
decipher 
The same postulate of an electron, as a physical entity, was 
arrived at by Lorentz and Larmor, on theoretical grounds. It 
is indeed implicitly contained in Maxwell’s theory. He gives 
two equations involving electric displacement ; one apparently 
appropriate to free ether, the _ to media containing free 
electricity. When this is interpreted in terms of the electron 
theory, it is found that the total: current (which is subject to 
the condition that the current of an incompressible fluid must 
satisfy) is found to be made up of a polarization current and an 
electronic current or current due to electrons in motion. It is 
further found that it is not necessary to regard magnetism as 
a separate entity at all but a condition of the ethereal medium 
ceive, in fact, issuing from the source of electro-magnetic 
energy, Faraday tubes which move through the medium at 
right angles to themselves along the line of energy-flow, with 
the velocity of light, as an essential constituent of the pheno- 
menon of radiation. And we may explain the associated pro- 
perties of magnetism by saying ‘‘that the disturbance 3 the 
i of ether exerts influence in the same general kind of way 
pressure, involved in the inertia of moving anid, con- 
mis the motion of the vortices or solid bodies which are 
