The present century was already well advanced before there was any
solid ground for the belief that the worlds of space are made of
analogous or identical materials. It was only with the invention of
the spectroscope and the analysis of light that the material identity
of universal nature was proved by methods which could not be doubted.
The proof came by the spectroscope.
This little instrument, though not famed as is its lordly kinsman the
telescope, or even regarded with the popular favor of the microscope,
has nevertheless carried us as far, and, we were about to say, taught
us as much, as either of the others. It is one thing to see the worlds
afar, to note them visibly, to describe their outlines, to measure
their mass and determine their motions. It is another thing to know
their constitution, the substances of which they are composed, the
material condition in which they exist and the state of their progress
in worldhood. The latter work is the task of the spectroscope; and
right well has it accomplished its mission.
The solar spectrum has been known from the earliest ages. When the
sun-bow was set on the background of cloud over the diluvial floods,
the living beings of that age saw a spectrum--the glorious spectrum of
rain and shine. Wherever the rays of light have been diffracted under
given conditions by the agency of water drops, prism of glass or other
such transparent medium, and the ray has fallen on a suitable screen,
lo! there has been the beautiful spectrum of light.
The artificial, intentional production of this phenomenon of light has
long been known, and both novice and scientist have tested and
improved the methods of getting given results. The child's soap-bubble
shows it in miniature splendor. The pressure of one wet pane of glass
against another reveals it. The breakage of nearly all crystalline
substances brings something of the colored effects of light; but the
triangular prism of glass, suitably prepared, best of all displays the
analysis of the sun-beam into the colors of which it is composed.
The spectroscope is the improved instrument by which the diffracting
prism is best employed in producing the spectrum. The reader no doubt
has seen a spectroscope, and has observed its beautiful work. In this
place we pass, however, from the instrument of production to the
spectrum, or analyzed result, as the same is shown on a screen. There
the pencil of white light falling from the sun is spread out in the
manner of a fan, presenting on the screen the following arrangement of
colors: red, orange, yellow, green, blue, indigo and violet.
This order of colors, beginning with red, starts from that side of the
spectrum which is least bent from the right line in which the white
ray was traveling. The violet rays are most bent. The red rays are
thus said to be at the _lower_ edge of the prism, and the violet rays
at the _upper_ edge. Below the red rays there are now known to be
certain invisible rays, as of heat and electricity. Above the violet
rays are other invisible rays, such as the actinic influence. In fact,
the spectrum, beginning invisibly, passes by way of the visible rays
to the invisible again. Nor can any scientist in the world say at the
present time _how much_ is really included in the spread-out fan of
analyzed sunlight.
Thus much scientists have known for some time. Certain other facts,
however, in connection with the solar spectrum are of greater
importance than are its more sensible phenomena. It was in the year
1802 that the English physicist, William Hyde Wollaston, discovered
that the solar spectrum is crossed with a large number of _dark
lines_. He it was who first mapped these lines and showed their
relative position. He it was also who discovered the existence of
invisible rays above the violet. Twelve years afterward Joseph von
Fraunhofer, of Munich, a German optician of remarkable talents, took
up the examination of the Wollaston lines, and by his success in the
investigation succeeded in attracting the attention of the world.
This second stage in scientific discovery is generally that which
receives the plaudits of mankind. It was so in the case of Fraunhofer.
His name was given to the dark lines in the solar spectrum, and the
nomenclature is retained to the present time. They are called the
"Fraunhofer lines." It was soon discovered that the lines in question
as produced in the spectrum are due to the presence of gases in the
producing flame or source of light. It was also discovered that each
substance in, the process of combustion yields its own line or set of
lines. These appear at regular intervals in the spectrum. When several
substances are consumed at the same time; the lines of each appear in
the spectrum. The result is a _system_ of lines, becoming more and
more complex as the number of elements in the consuming materials is
increased.
The lines in a narrow spectrum fall so closely together that they
cannot be critically examined; but when more than one prism is used
and the spectrum by this means spread out widely, the dark lines are
made to stand apart. They are then found to number many thousands. We
speak now of the analysis of sunlight. Experimentation was naturally
turned, however, to terrestrial gases and solids on fire, and it was
found that these also produce like series of dark lines in the
spectrum. Or when the substances are consumed _as solids_, then the
spectral effects are reversed, and the lines that would be dark lines
in the luminous colored spectrum become themselves luminous lines on
the screen; but these lines hold the same relation in mathematical
measurement, etc., as do the _dark_ lines in the colored spectrum.
Skillful spectroscopists succeeded in detecting and delineating the
lines that were peculiar to each substance. By burning such substances
in flame, they were able to produce the lines, and thus verify
results. By such experimentation the various lines present in the
solar spectrum were separated from the complex result, and the
conclusion was reached that in the burning surface of the sun certain
substances _well known on earth are present_; for the lines of those
substances are shown in the spectrum.
No other known substances would produce the given lines. The
conclusion is overwhelming that the substances in question are present
in a gaseous condition in the burning flames of the sun. Down to the
present time the examination of the sun's atmosphere has shown the
existence therein of thirty-six known elements. These include sodium,
potassium, calcium, magnesium, iron, copper, cobalt, silver, lead,
tin, zinc, titanium, aluminium, chromium, silicon, carbon, hydrogen
and several others.
It was thus established that in the constitution of the sun many of
the well-known elements of the earth are present. There could be no
mistake about it. An identity of lines in such a case proved beyond
dispute the identity of the substance from which such lines are
derived. The existence of common materials in the central sphere of
our system and in _one_ of his attendant orbs--our own--could not be
doubted. The discovery of such a fact led by immediate inference to
the expectation and belief that the _other_ planets were of like
constitution, or in a word, that the whole solar system was
essentially composed of identical materials.
As the inquiry proceeded, it was found, however, that the agreement
in the lines of different spectra was not perfect. Lines would be
found in the spectrum derived from one source that were not present in
a spectrum derived from another source. Materials were therefore
suggested as present in one body that were not present in another.
Still further inquiry confirmed the belief that while there is a
general uniformity in the materials of our solar system, the identity
is not complete in all. An element is found in one part that may not
be found in another. Hydrogen shows its line in the spectrum derived
from every heavenly body that has been investigated; but not so
aluminium or cobalt. Sodium, that is, the salt-producing base, is
discovered everywhere, but not nickel or arsenium. The result, in a
word, shows a certain variability in the distribution of solar and
planetary matter, but a general identity of most.
The question next presented itself as to the character of the luminous
bodies _beyond_ the solar system. Of what kind of matter are the
comets? Of what kind are the fixed stars? Of what kind are the nebulæ?
Could the spectroscope be used in determining also the character of
the materials in those orbs that we see shining in the depths of
space? The instrument was turned in answer to these questions to the
sidereal heavens. No other branch of science has been prosecuted in
the after half of this century with more zeal and success than has the
spectroscopic analysis of the fixed stars. These are known by the
telescope to have the character of suns. The most general fact of the
visible heavens is the plentiful distribution of suns. They sparkle
everywhere as the so-called fixed stars. To them the telescope has
been virtually turned in vain. We say in vain because no single fixed
star has, we believe, ever been made by aid of the telescope to show a
disc.
On turning the telescope to a fixed star, its brightness, its
brilliancy, increases according to the power of the instrument. Coming
into the field of one of these great suns of space, the telescope
shows a miraculous dawn spreading and blazing into a glorious sunrise,
and a sun itself flaming like infinite majesty on the sight; but there
is no disc--nothing but a blaze of glory. Thus in a sense the
telescope has worked in vain on the visible heavens. But not so the
spectroscope. The latter has done its glorious work. Turning to a
given fixed star, it shows that the tremendous combustion going on
therein is virtually the same as that in our own sun. There, too, is
flaming hydrogen, and there is carbon and oxygen and iron and sodium
and potassium and many other of the leading elements of what we thus
know to be universal nature. The suns are all akin; they are
cousins-german. They are of the same family--they and their progeny.
They were born of the same universal fact. They are of the same
Father! They are builded on the same plan, and they have a common
destiny. Aye, more, the nebulæ that float far off, swanlike, in the
infinitudes, are of the same family. The nebulæ may be regarded as the
mothers of universes. It is out of their bosoms that the life and
substance of all suns and worlds are drawn! And these, too, are
composed of the common matter of universal nature. It is the same
matter that we eat and drink. It is the same that we breathe. It is
the same that we see aflame in our lamps and grates. It is the same
that is borne to us in the fragrance of flowers planted on the graves
of our dead. It is the common hydrogen and carbon and oxygen and
nitrogen of our earth and its envelope. It is the soda of our bread;
the potassa of our ashes; the phosphorus of our bones and brain!
Indeed, the universe throughout is of one form and one substance, and
there is one Father over all. Sooner or later the concepts of science
and of religion will come together; and the small agitations and
conflicts of human thought and hope will pass away in a sublime unity
of human faith.
Progress in Discovery and Invention.