out 186,000 miles a
second. As the sun is about 94,000,000 miles from the earth, it takes
8-1/2 minutes for the light of the sun to reach us.

REFLECTION.--One of the most important things connected with light is
that of reflection. It is that quality which is utilized in telescopes,
microscopes, mirrors, heliograph signaling and other like apparatus and
uses. The underlying principle is, that a ray is reflected, or thrown
back from a mirror at the same angle as that which produces the light.

When the rays of the sun, which are, of course, parallel, strike a
concave mirror, the reflecting rays are converged; and when the rays
strike a convex mirror they diverge. In this way the principle is
employed in reflecting telescopes.

REFRACTION.--This is the peculiar action of light in passing through
substances. If a ray passes through water at an angle to the surface the
ray will bend downwardly in passing through, and then again pass on in a
straight line. This will be noticed if a pencil is stood in a glass of
water at an angle, when it will appear bent.

Refraction is that which enables light to be divided up, or analyzed. In
this way white light from the sun is shown to be composed of seven
principal colors.

COLORS.--If the light is passed through a prism, which is a triangularly
shaped piece of glass, the rays on emerging will diverge from each
other, and when they fall on a wall or screen the colors red, orange,
yellow, green, blue, indigo and violet are shown.

The reason for this is that the ray in passing through the prism has the
different colors in it refract at different angles, the violet bending
more than the red.

THE SPECTROSCOPE.--The ability to make what is thus called a _spectrum_,
brought forth one of the most wonderful instruments ever devised by man.
If any metal, or material, is fused, or put in such a condition that a
ray of light can be obtained from it, and this light is passed through a
prism, it will be found that each substance has its own peculiar
divisions and arrangements of colors.

In this way substances are determined by what is called _spectrum
analysis_, and it is by means of this instrument that the composition of
the sun, and the planets and fixed stars are determined.

THE RAINBOW.--The rainbow is one of the effects of refraction, as the
light, striking the little globular particles of water suspended in the
air, produces a breaking up of the white light into its component