1901 - 2 .] Mr J. Fraser on Constitution of Matter and Ether. 33 
to clearly conceive of it being formed of anything else — then a 
wave of heat or light (the undulatory theory being conceded) 
consists of a condensation, or a crowding together, of a more or 
less number of particles, all at the same distance from the source 
of the wave, or point of disturbance, followed by a dilatation or 
spreading out of the particles, — in fact, a spherical shell of con- 
densed ether, followed by another of dilated ether, spreading out, 
like the circular waves on a pond surrounding the point disturbed 
by a stone, in every direction in space. But as they spread out 
they dwindle in amplitude, and the further they spread the more 
they dwindle, till at last they can dwindle no further, having reached 
the point where the shell or condensation would be only one 
particle thick, or where there would be only one particle left on 
the front or crest of the wave moving by itself and giving up its 
motion to its neighbour, and so on continually. At this point the 
wave would cease to exist as such, but the single-particle motion 
would go on for ever, or until it was absorbed in doing some 
work. The spherical shell would be no longer continuous — 
would break, in fact — but the amount of motion would be the 
same as at the start.* At the start, the particles partaking in the 
motion would be all crowded together close to the surface of the 
luminous body. At the end of the existence of the leave , who 
shall say how many thousands of billions of miles separate the 
particles to which the motion has been transmitted? Now, every 
wave of heat or light in the universe, if not absorbed in doing 
work, must at last result in this degraded form ; and as the universe 
of stars is, at least practically, infinite, there must be in space a 
practically infinite amount of these single-particle motions equal in 
amount from every direction; motion from one direction being 
* After the condensation, or shell, was reduced to a single particle in thick- 
ness, the motion still continuing, as it must, the particles to which the motion 
has been transmitted can no longer be neighbours, but gradually get separated, 
till at last they may be any distance apart. So that the motions which 
generate the pressure in the ether, and in which contiguous particles are 
engaged, may be generated in opposite quarters of the universe. And these 
motions can no longer be wave motions, for the latter consist in a 
simultaneous motion of all the particles, at the same distance from the point 
of disturbance of the medium, in the same direction ; but the pressure motions 
being generated at all distances, in opposite directions, act on each particle 
independently, and thus subject the medium to simultaneous and contrary 
motions, and which generate the intense pressure. 
PROC. ROY. SOC. EDIN. — VOL. XXIV. 
3 
