d the margin, or better
still, if nearer the margin, when the spots lie more edgeways to the
eye, I can see distinctly the relative thickness of the photosphere and
the underlying dusky penumbra, which lie on contiguous planes of about
equal thickness, like the coatings of an onion. When these spots are
nearer the centre of the sun, we see more vertically into their depths,
by which I frequently observe a third or cloud stratum, underlying the
penumbra, and partially closing the opening, doubtless to screen the
underlying globe (which, by contrast with the photosphere, is intensely
black) from excessive light, or to render it more diffusive.[11] The
concentric faculae are then plainly visible, and do not appear to rise
above the surface of the photosphere (as generally described), but
rather as depressions in that luminous envelope, frequently breaking
entirely through to the penumbra; and when this last parts, forms what
are called 'spots.' The delusion in supposing the faculae to be elevated
ridges, appears to me to be owing to the occasional depth of the faculae
breaking down through the photosphere to the dusky penumbra, giving the
appearance of a shadow from an elevated ridge. What is still more
interesting, in a favorable state of the atmosphere, I can distinctly
see over the _whole_ surface of the sun, not occupied by large spots or
by faculae, a network of pores or minute spots in countless numbers, with
dividing lines or faculae-like depressions in the photosphere, separating
each little hole, varying in size, some sufficiently large to exhibit
irregularities of outline, doubtless frequently combining and forming
larger spots.[12] When there are no scintillations in the air, the rim
or margin of the sun appears to be a perfect circle, as defined, in
outline, as if carved. By interposing an adjusted circular card, to cut
off the direct rays of the sun, thus improvising an eclipse, not a stray
ray of light is seen to dart in any direction from the sun, except what
is reflected to the instrument, diffusively, from our atmosphere; thus
proving that the corona, the coruscations or flashes of light, seen
during a total or nearly total eclipse of the sun by the moon, are not
rays direct from the sun, but reflections from lunar snow-clad
mountains, into her highly attenuated atmosphere. Solar light, being
electric, is not developed as light until reaching the atmosphere of a
planet or satellite, or their more solid subst