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 time, is to be ultimately
abolished by the agency which produced it. In the words of our
authors, "If the visible universe be developed from an invisible
which is not a perfect fluid, then the argument deduced by Sir
William Thomson in favour of the eternity of ordinary matter
disappears, since this eternity depends upon the perfect fluidity
of the invisible. In fine, if we suppose the material universe to
be composed of a series of vortex-rings developed from an
invisible universe which is not a perfect fluid, it will be
ephemeral, just as the smoke-ring which we develop from air, or
that which we develop from water, is ephemeral, the only
difference being in duration, these lasting only for a few
seconds, and the others it may be for billions of years." Thus,
as our authors suppose that "the available energy of the visible
universe will ultimately be appropriated by the invisible," they
go on to imagine, "at least as a possibility, that the separate
existence of the visible universe will share the same fate, so
that we shall have no huge, useless, inert mass existing in after
ages to remind the passer-by of a form of energy and a species of
matter that is long since out of date and functionally effete.
Why should not the universe bury its dead out of sight?"

In one respect perhaps no more stupendous subject of
contemplation than this has ever been offered to the mind of man.