end here. There remains to be
noticed a more conspicuous and still more significant fact. If the Solar
System was produced by the concentration of diffused matter, which
evolved heat while gravitating into its present dense form; then there
is an obvious implication. Other things equal, the latest-formed mass
will be the latest in cooling--will, for an almost infinite time,
possess a greater heat than the earlier-formed ones. Other things equal,
the largest mass will, because of its superior aggregative force, become
hotter than the others, and radiate more intensely. Other things equal,
the largest mass, notwithstanding the higher temperature it reaches,
will, in consequence of its relatively small surface, be the slowest in
losing its evolved heat. And hence, if there is one mass which was not
only formed after the rest, but exceeds them enormously in size, it
follows that this one will reach an intensity of incandescence far
beyond that reached by the rest; and will continue in a state of intense
incandescence long after the rest have cooled. Such a mass we have in
the Sun. It is a corollary from the Nebular Hypothesis, that the matter
forming the Sun assumed its present integrated shape at a period much
more recent than that at which the planets became definite bodies. The
quantity of matter contained in the Sun is nearly five million times
that contained in the smallest planet, and above a thousand times that
contained in the largest. And while, from the enormous gravitative force
of his parts to their common centre, the evolution of heat has been
intense, the facilities of radiation have been relatively small. Hence
the still-continued high temperature. Just that condition of the central
body which is a necessary inference from the Nebular Hypothesis, we find
actually existing in the Sun.

[The paragraph which here follows, though it contains some questionable
propositions, I reproduce just as it stood when first published in 1858,
for reasons which will presently be apparent.]

It may be well to consider more closely, what is the probable condition
of the Sun's surface. Round the globe of incandescent molten substances,
thus conceived to form the visible body of the Sun [which in conformity
with the argument in a previous section, now transferred to the Addenda,
was inferred to be hollow and filled with gaseous matter at high
tension] there is known to exist a voluminous atmosphere: the inferior
brilliancy of th