36 
Proceedings of Royal Society of Edinburgh. [sess. 
ginning, it is out of the ether I propose to construct all the matter 
of our experience. Now, in the beginning, to prevent confusion, 
I propose to call the unit of ether a particle , and the unit of 
ordinary matter an atom, a molecule being two or more atoms 
united together, as in the science of chemistry. Well, now, how 
are we to construct these atoms of chemistry out of the particles 
of the ether so that they shall exhibit all their chemical and 
physical peculiarities, such as “attraction of cohesion,” “chemical 
affinity,” “valency,” etc. ; also, and above all, motion through the 
ether without resistance and ‘ 1 attraction of gravity ” in pro- 
portion to mass? If we suppose the ethereal particles to be 
gathered together into little masses in proportion to the atomic 
weights, with what qualities are we to endow them so as to enable 
them to preserve their identity under all conditions ; and also, as 
I propose to utilise the pressure of the ether for the solution of 
this enigma, how arrange the particles so that gravity shall be 
exactly proportional to mass, i.e., so that each particle shall be 
subjected to exactly the same pressure ? I believe there is one 
way, and but one way only, by which this may be done, and that 
is, to endow the constituent ethereal particles of each atom with 
motion athwart the direction of the pressure in the medium ; in 
the same way as the planets are endowed with motion athwart the 
direction of the sun’s so-called attraction, and in such sort that 
they shall revolve round and round a vacuous space, and so closely 
set together or otherwise endowed with so much motion as to 
preclude the possibility of any of the particles of the medium 
penetrating the vacuum. In fact, a veritable ethereal bubble. 
Yes ; but a bubble, the skin of which, unlike a soap-bubble, is 
only one particle thick ; and also unlike a soap-bubble, in 
that inside there is perfect emptiness — an absolute vacuum ; and 
also unlike it, in that all the particles forming the film are in 
rapid motion in great circles round the vacuum. Of course, in a 
bubble of this kind there would be innumerable collisions between 
the revolving particles. Indeed, if they happened to be very 
closely set, a particle might take a very long time in going round 
the bubble, or for that matter it might never go round it at all ; all 
that is essential is that the motion of each should be fully trans- 
ferred to its neighbours, and by them to be retransferred in every 
