utions to solar
science. The cloud-like character which he attributed to the radiant
shell of the sun (first named by Schroeter the "photosphere") is borne
out by all recent investigations; he observed its mottled or corrugated
aspect, resembling, as he described it, the roughness on the rind of an
orange; showed that "faculae" are elevations or heaped-up ridges of the
disturbed photospheric matter; and threw out the idea that spots may
ensue from an excess of the ordinary luminous emissions. A certain
"empyreal" gas was, he supposed (very much as Wilson had done),
generated in the body of the sun, and rising everywhere by reason of its
lightness, made for itself, when in moderate quantities, small openings
or "pores,"[141] abundantly visible as dark points on the solar disc.
But should an uncommon quantity be formed, "it will," he maintained,
"burst through the planetary[142] regions of clouds, and thus will
produce great openings; then, spreading itself above them, it will
occasion large shallows (penumbrae), and mixing afterwards gradually with
other superior gases, it will promote the increase, and assist in the
maintenance, of the general luminous phenomena."[143]

This partial anticipation of the modern view that the solar radiations
are maintained by some process of circulation within the solar mass, was
reached by Herschel through prolonged study of the phenomena in
question. The novel and important idea contained in it, however, it was
at that time premature to attempt to develop. But though many of the
subtler suggestions of Herschel's genius passed unnoticed by his
contemporaries, the main result of his solar researches was an
unmistakable one. It was nothing less than the definitive introduction
into astronomy of the paradoxical conception of the central fire and
hearth of our system as a cold, dark, terrestrial mass, wrapt in a
mantle of innocuous radiance--an earth, so to speak, within--a sun
without.

Let us pause for a moment to consider the value of this remarkable
innovation. It certainly was not a step in the direction of truth. On
the contrary, the crude notions of Anaxagoras and Xeno approached more
nearly to what we now know of the sun, than the complicated structure
devised for the happiness of a nobler race of beings than our own by the
benevolence of eighteenth-century astronomers. And yet it undoubtedly
constituted a very important advance in science. It was the first
earnest attempt to bring