28 YRESIDENT’S ADDRESS—SECTION A. 
tion of continuity, viz., that the portion of fluid forming a vortex 
filament with motion of a definite character must for ever con- 
tinue, as its constituent element would, in tri-dimensional space, 
be violated by untying a knot or separating the rings. 
It is evident that with a few elementary types a large number 
of different forms of vortex structures can be invented by knot- 
ting and linking, so that the theory is credited with being 
resourceful with respect to its possibilities in the matter of struc- 
tural variety. 
Vortices of the closed curve type have peculiar vibrational 
properties. If not knotted the closed curve vortex has the 
circular ring for its form of equilibrium, and if at any instant it 
has any other form, it will be subject to vibrational motion, a 
result which may also arise from collisions. For example, in 
an elliptical ring the magnitudes of the axes will alternate. 
Thus its vibrational complexity is adequate in regard to the evi- 
dence afforded by the spectroscope of the behaviour of the mole- 
cules of elements in the state of incandescence. The molecule 
or atom so constituted is supposed to be dynamically indis- 
cerptible and impenetrable, and consequently indestructible. 
21. Matter as a Mode of Motionin a Hypothetical Substance. 
—According to this theory, then, the plenum, or protyle, is the 
ether, a purely supersensible substance; it has mass, whatever 
that may mean, consistently with the other elements of the con- 
ception, a point to which further reference will be made. Atoms, 
molecules, and material bodies, with their complex properties, 
and their mysterious relation to consciousness, are simply 
elaborate congeries of extremely minute vortices therein ; that 
is to say, as to substance, they are ether itself, but ct 1s not the 
substance which constitutes them atoms, it is the mode of motion 
an the substance. 
From the philosophical point of view this is not essentially 
different in respect of its ultimate features from the conception 
of Descartes, and appears to be little more than a fusion of the 
ideas of Descartes’ infinitely extended substance and Helmholtz’s 
vortices. It may here be incidentally mentioned that Clerk- 
Maxwell realised that if the property of mass be transferred to the 
ether, then the inertia of bodies built up of vortex rings has to 
be deduced. How far this becomes a purely a priort method 
of procedure, and valid from the point of view of those who take 
the phzenomena of Nature as data to be explained by knowledge 
experimentally justified, or verified, is worthy of further con- 
sideration. 
The vortex-atom theory is remarkable as having been put 
forward to proye—historico-mathematically as it were—a crea- 
tive act (a). 
(a) The Unseen Universe. 
