stitution during the session of 1880. Discussing the conditions under
which, if "our so-called elements are compounded of elemental matter",
they may have been formed, Prof. Dewar, arguing from the known habitudes
of compound substances, concludes that the formation is in each case a
function of pressure, temperature, and nature of the environing gases.]

[Footnote 23: At the date of this passage the established teleology made
it seem needful to assume that all the planets are habitable, and that
even beneath the photosphere of the Sun there exists a dark body which
may be the scene of life; but since then, the influence of teleology has
so far diminished that this hypothesis can no longer be called the
current one.]

[Footnote 24: It may here be mentioned (though the principal
significance of this comes under the next head) that the average mean
distance of the later-discovered planetoids is somewhat greater than
that of these earlier-discovered; amounting to 2.61 for Nos. 1 to 35 and
2.80 for Nos. 211 to 245. For this observation I am indebted to Mr.
Lynn; whose attention was drawn to it while revising for me the
statements contained in this paragraph, so as to include discoveries
made since the paragraph was written.]

THE CONSTITUTION OF THE SUN.

[_First published in_ The Reader _for February_ 25, 1865. _I
reproduce this essay chiefly to give a place to the speculation
concerning the solar spots which forms the latter portion of it._]

The hypothesis of M. Faye, described in your numbers for January 28 and
February 4, respectively, is to a considerable extent coincident with
one which I ventured to suggest in an article on "Recent Astronomy and
the Nebular Hypothesis," published in the _Westminster Review_ for July,
1858. In considering the possible causes of the immense differences of
specific gravity among the planets, I was led to question the validity
of the tacit assumption that each planet consists of solid or liquid
matter from centre to surface. It seemed to me that any other internal
structure which was mechanically stable, might be assumed with equal
legitimacy. And the hypothesis of a solid or liquid shell, having its
cavity filled with gaseous matter at high pressure and temperature [and
of great density], was one which seemed worth considering.

Hence arose the inquiry--What structure will result from the process of
nebular condensation? [Here followed a long speculation respec