produced in the place of the coloured band
belonging to the combustion of some element at
the moment when an exceedingly intense light,
such as that emitted by the burning lime, is
made to pass through a much less intense light
coloured by the burning of that element. This
particular line is, in fact, only dark by contrast
with greater light. The ray of intense white
light that would have passed into the prism and
been decomposed into its colours is modified
by the exceedingly fainter rays of yellow light
through which the white light passes.

Exactly as it is with the sodium in common
salt, so would it be, and so must it be, with
other substances. If the white light passes
through the coloured flame, then that part of
the complete spectrum that would have been
coloured if there had been no intense light
shining behind it, are simply dark when this
greater light is present—a result that could
hardly have been anticipated, though not
incapable of explanation according to that theory of
light, which assumes light to consist of waves
rather than of substantial and material emanations.

We are now in a position to advance the
required step, and apply what has been discovered
to explain the cause of those dark lines that we
know to exist in the solar spectrum. By actual
experiment, the positions of nearly a hundred
dark lines in the spectrum have been identified
with those colour rays resulting from the
combustion of some metals well known and easily
procurable on the earth, a prismatic spectrum
crossed by those particular lines already marked
by Fraunhofer being obtained in the spectrum
arising from the decomposition of the Drummond
light when that light is allowed to shine
through flames produced by burning the metals
in question. Since these lines are characteristic
of the metals, there can only be one conclusion,
which may be thus expressed: The light from
the sun is emitted from a central nucleus of
intense brightness, and shines through a clouded
atmosphere of coloured flame containing a number
of metals identical with those on our earth.

For if the sun's atmosphere alone shone, its
nucleus being dark, the light, however intense,
would be made up of the colours produced by
the burning of the metals, and would give bright
lines where there are now dark ones. It is only
because the light from the nucleus is so
surpassingly brighter than that of the coloured
flame that forms the sun's atmosphere that
these shaded lines, which are really faint lines
of colour, can be at all discovered.

What would have been Newton's feelings had
it been given to him to contemplate this
marvellous deduction from his discovery of the
composition of light? By analysis of light, we obtain
a degree of accuracy in investigations concerning
the presence or absence of particular substances
beyond all comparison greater than had hitherto
been thought possible. But we also analyse by
the same means the actual material of the solar
atmosphere, and we may look forward even to
compare the light of the fixed stars with that
obtained from the sun, and thus decide also as
to their atmospheres of flame.

The distances of these bodies are indeed so
great as to defy anything like a correct conception,
although we may state it in words and
figures. But the light that takes years to reach
us seems to pass unscathed through all that vast
space that intervenes; and even if it should
appear that there are interruptions produced by a
thin ether, through which all light passes, we may
still expect to compare results. Thus, if there
be in the light any of these dark lines that
belong to an interrupting atmosphere, we shall
be able to discover by actual observation whether
these lines are or are not identical with those
produced by known vapours on the earth or sun.
We may even learn whether the matter of which
our system is composed is the same as other
matter distributed through space, or whether
there may be in the infinite distance new
elements and combinations of which we can know
nothing.

Newton, indeed, as we have said, could not look
forward to this gradual working out of the
discovery he originated. In itself one of the most
elegant and complete explanations of the source of
so much that is beautiful in nature, his
prismatic spectrum has in modern hands laid the
foundation of a new science, and has in the
most unexpected manner offered its aid to
chemistry just at the point where chemical
analysis seemed to fail.

In the most delicate, the most difficult, and
the most obscure of those processes of chemistry,
where infinite caution is always necessary
to avoid a false conclusion, the observer in
physical science steps in with accurate measurement
and almost unerring power to suggest a
means of comparison whose certainty is only
paralleled by its perfect simplicity.

Two new metals have been already detected
by examining the coloured flame obtained by
burning the residuum after evaporating certain
mineral waters. Both these are alkaline metals
resembling in their properties sodium and
potassium; and their existence once made known
by this new analysis, they have since been
obtained in small quantities by more ordinary
methods for further examination. It may be
expected that other instances will be detected
in a similar way before long.

We owe to two German chemists the recognition
of the value and importance of this
method of analysis, and some of the ingenious
contrivances required to effect it. They are
both eminent in their respective departments of
science, and are still labouring in the same field.
Professors Kirchhoff and Bunsen, of Heidelberg,
will ever be remembered as among those who
have made a distinct advance in experimental
science.

The step made by Newton in discovering
the compound nature of light seemed at the
time to close the whole subject; and even when
the dark bands in the spectrum were noticed,
they seemed so likely to be the consequence of
partial absorption in our own atmosphere, that