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 spr