of something like 70 miles per minute.” But it is admitted 
that this flying about of particles does not do work properly 
unless it be supplemented by “ quid ance } ’ applied to some of 
the particles by the finite intelligence of certain “ demons ” 
( U.JJ . , Arts. 111-112, pp. 87-89). Added to all this, Professor 
Sir William Thomson says that we are to conceive of these 
particles as being simple, or involved “vortex-rings,” which 
are strictly atoms, because having the property of “ wriggling” 
they cannot be cut (77. 77., Art. 133, p. 103). This conception 
of the form and qualities of the atom is derived solely from 
the solution of a hydro dynamical problem by Helmholtz, from 
which, in the opinion of Professor Thomson, there results 
vortex-motion of so absolutely unalterable a character that if 
the atom be taken to be a vortex-ring, an argument might 
thence be deduced “ in favour of the eternity of ordinary 
matter.” (See Z7. 77., Art. 152, p. 118.) Having for many 
years bestowed particular attention on hydrodynamical ques- 
tions, I might, if the occasion permitted, dispute the validity 
of this interpretation of Helmholtz's solution, and, at all events, 
call in question the applicability of his reasoning to determine 
the ultimate form and destination of matter. But it will 
suffice for my present purpose only to remark that a system of 
philosophy which arrives at the qualities of the atom by means 
of an abstruse piece of mixed mathematics is utterly at variance 
with the Newtonian rule of defining an atom in terms intelli- 
gible from the common sense and experience of mankind, the 
reality of the hypothetical atom being left for decision by an 
adequate number of comparisons of results obtained by mathe- 
matical reasoning based on this and related definitions with 
matters of fact. 
19. The foregoing exposition of the character and results of 
this novel scheme of physical philosophy will, I hope, enable 
members of the Institute interested in these questions to form 
a judgment of the weight to be given to views which the 
upholders of such philosophy may express in opposition to the 
argument with which I am about to follow up the preceding 
introductory considerations. For my part, I have no hesitation 
in saying, that, according to my judgment, the arbitrary specu- 
lations detailed above, and the inferences drawn from them, 
go quite beyond the limits of sober philosophy. Now it may 
be asserted that the course taken by these physicists is avowedly 
a departure from the Newtonian abstract principles of “Natural 
Philosophy,” the adoption of which forms an essential part of 
my argument. Hence, since it appears that mathematical 
physicists of undoubted ability, who have rejected those prin- 
ciples, have been conducted by a course of empirical reasoning 
