interrogatory. "Is it not reasonable to think," he
asks, "that the great and stupendous body of the sun is made up of two
kinds of matter, very different in their qualities; that by far the
greater part is solid and dark, and that this immense and dark globe is
encompassed with a thin covering of that resplendent substance from
which the sun would seem to derive the whole of his vivifying heat and
energy?"[139] He further suggests that the excavations or spots may be
occasioned "by the working of some sort of elastic vapour which is
generated within the dark globe," and that the luminous matter, being in
some degree fluid, and being acted upon by gravity, tends to flow down
and cover the nucleus. From these hints, supplemented by his own
diligent observations and sagacious reasonings, Herschel elaborated a
scheme of solar constitution which held its ground until the physics of
the sun were revolutionised by the spectroscope.

A cool, dark, solid globe, its surface diversified with mountains and
valleys, clothed in luxuriant vegetation, and "richly stored with
inhabitants," protected by a heavy cloud-canopy from the intolerable
glare of the upper luminous region, where the dazzling coruscations of a
solar aurora some thousands of miles in depth evolved the stores of
light and heat which vivify our world--such was the central luminary
which Herschel constructed with his wonted ingenuity, and described with
his wonted eloquence.

"This way of considering the sun and its atmosphere," he says,[140]
"removes the great dissimilarity we have hitherto been used to find
between its condition and that of the rest of the great bodies of the
solar system. The sun, viewed in this light, appears to be nothing else
than a very eminent, large, and lucid planet, evidently the first, or,
in strictness of speaking, the only primary one of our system; all
others being truly secondary to it. Its similarity to the other globes
of the solar system with regard to its solidity, its atmosphere, and its
diversified surface, the rotation upon its axis, and the fall of heavy
bodies, leads us on to suppose that it is most probably also inhabited,
like the rest of the planets, by beings whose organs are adapted to the
peculiar circumstances of that vast globe."

We smile at conclusions which our present knowledge condemns as
extravagant and impossible, but such incidental flights of fancy in no
way derogate from the high value of Herschel's contrib