ch agrees completely with the processes here supposed. He says:--

"There is nothing which represents so faithfully this appearance as
the slow subsidence of some flocculent chemical precipitates in a
transparent fluid, when viewed perpendicularly from above: so
faithfully, indeed, that it is hardly possible not to be impressed
with the idea of a luminous medium intermixed, but not confounded,
with a transparent and non-luminous atmosphere, either floating as
clouds in our air, or pervading it in vast sheets and columns like
flame, or the streamers of our northern lights".--_Treatise on
Astronomy_, p. 208.

If the constitution of the Sun be that which is above inferred, it does
not seem difficult to conceive still more specifically the production of
these appearances. Everywhere throughout the atmosphere of metallic
vapours which clothes the solar surface, there must be ascending and
descending currents. The magnitude of these currents must obviously
depend on the depth of this atmosphere. If it is shallow, the currents
must be small; but if many thousands of miles deep, the currents may be
wide enough to render visible to us the places at which they severally
impinge on the limit of the atmosphere, and the places whence the
descending currents commence. The top of an ascending current will be a
space over which the thickness of condensed cloud is the least, and
through which the greatest amount of light from beneath penetrates. The
clouds perpetually formed at the top of such a current, will be
perpetually thrust aside by the uncondensed gases from below them; and,
growing while they are thrust aside, will collect in the spaces between
the ascending currents, where there will result the greatest degree of
opacity. Hence the mottled appearance--hence the "pores," or dark
interspaces, separating the light-giving spots.[25]

Of the more special appearances which the photosphere presents, let us
take first the faculae. These are ascribed to waves in the photosphere;
and the way in which such waves might produce an excess of light has
been variously explained in conformity with various hypotheses. What
would result from them in a photosphere constituted and conditioned as
above supposed? Traversing a canopy of cloud, here thicker and there
thinner, a wave would cause a disturbance very unlikely to leave the
thin and thick parts without any change in their average permeability to