hat the material atom can
no longer be regarded as absolutely indestructible, but only as
indefinitely enduring. It may have been generated, in bygone eternity,
by a natural process of evolution, and in future eternity may come to an
end. Relatively to our powers of comprehension the practical difference
is perhaps not great. Scientifically speaking, Helmholtz and Thomson
are as well entitled to reason upon the assumption of a perfectly
frictionless fluid as geometers in general are entitled to assume
perfect lines without breadth and perfect surfaces without thickness.
Perfect lines and surfaces do not exist within the region of our
experience; yet the conclusions of geometry are none the less true
ideally, though in any particular concrete instance they are only
approximately realized. Just so with the conception of a frictionless
fluid. So far as experience goes, such a thing has no more real
existence than a line without breadth; and hence an atomic theory based
upon such an assumption may be as true ideally as any of the theorems
of Euclid, but it can give only an approximatively true account of
the actual universe. These considerations do not at all affect the
scientific value of the theory; but they will modify the tenour of
such transcendental inferences as may be drawn from it regarding, the
probable origin and destiny of the universe.

The conclusions reached in the first part of this paper, while we were
dealing only with gross visible matter, may have seemed bold enough; but
they are far surpassed by the inference which our authors draw from the
vortex theory as they interpret it. Our authors exhibit various reasons,
more or less sound, for attributing to the primordial fluid some slight
amount of friction; and in support of this view they adduce Le Sage's
explanation of gravitation as a differential result of pressure,
and Struve's theory of the partial absorption of light-rays by the
ether,--questions with which our present purpose does not require us
to meddle. Apart from such questions it is every way probable that the
primary assumption of Helmholtz and Thomson is only an approximation
to the truth. But if we accredit the primordial fluid with even an
infinitesimal amount of friction, then we are required to conceive of
the visible universe as developed from the invisible and as destined to
return into the invisible. The vortex-atom, produced by infinitesimal
friction operating through wellnigh infinite