as scoriae floating on a liquid surface, and ejected from
solar volcanoes, of which the burning mountains of the earth convey
but a feeble idea. Hence observations become necessary as to the
nature of the incandescent matter of the sun; and when we remember the
immense distance of that body, such an attempt may well appear to be
one of temerity.

The progress of optical science, however, has given us the means of
determining this apparently insoluble question. It is well known, that
physicists are enabled at present to distinguish two kinds of
light--natural light and polarised light. A ray of the former exhibits
the same properties on any part of its form; not so the latter. A
polarised ray is said to have sides, and the different sides have
different properties, as demonstrated by many interesting phenomena.
Strange as it may seem, these rays thus described as having sides,
could pass through the eye of a needle by hundreds of thousands
without disturbing each other. Availing themselves, therefore, of the
assistance of polarised light, and an instrument named the
polariscope, or polarising telescope, observers obtain a double image
of the sun, both alike, and both white; but on reflecting this image
on water, or a glass mirror, the rays become polarised; the two images
are no longer alike or white, but are intensely coloured, while their
form remains unchanged. If one is red, the other is green, or yellow
and violet, always producing what are called the complementary
colours. With this instrument, it becomes possible to tell the
difference between natural and polarised light.

Another point for consideration is, that for a long time it was
supposed, that the light emanating from any incandescent body always
came to the eye as natural light, if in its passage it had not been
reflected or refracted. But experiment by the polariscope shewed, that
the ray departing from the surface at an angle sufficiently small was
polarised; while at the same time, it was demonstrated that the light
emitted by any gaseous body in flame--that of street-lamps, for
instance--is always in the natural state, whatever be its angle of
emission. From these remarks, some idea will be formed of the process
necessary to prove whether the substance which renders the sun visible
is solid, liquid, or gaseous. On looking at the sun in the
polariscope, the image, as before observed, is seen to be purely
white--a proof that the medium through which t