pe as little cloudlets of hazy light. One after
another were resolved into stars; and the natural conclusion was,
that all would yield and reveal themselves to be clustered suns,
when we had telescopes of sufficient power. But the spectroscope,
seeing not merely form but substance also, shows that some of them
are not stars in any sense, but masses of glowing gas. Two of these
nebulae are visible to the naked eye: one in Andromeda (see Fig.
68), and one around the middle star of the sword of Orion, shown
in Fig.78. A three-inch telescope resolves th Orionis into the
famous trapezium, and a nine-inch instrument sees two stars more.
The shape of the nebula is changeable, and is hardly suggestive of
the moulding influence of gravitation. It is probably composed of
glowing nitrogen and hydrogen gases. Nebulae are of all conceivable
shapes--circular, annular, oval, lenticular, [Page 218] conical,
spiral, snake-like, looped, and nameless. Compare the sprays of the
Crab nebulae above z Tauri, seen in Fig. 79, and the ring nebula,
Fig. 80. This last possibly consists of stars, and is situated, as
shown in Fig. 81, midway between b and g Lyrae.

[Illustration: Fig. 78.--The great Nebula about the multiple Star
th Orionis. (See Frontispiece.)]

When Herschel was sweeping the heavens with his telescope, and
saw but few stars, he often said to his assistant, "Prepare to
write; the nebulae are coming." They are most abundant where the
stars are least so. A zone about the heavens 30 deg. wide, with the
Milky Way in the centre, would include one-fourth of the celestial
sphere; but instead of one-fourth, we find nine-tenths
[Page 219]
of the stars in this zone, and but one-tenth of the nebulae.

These immense masses of unorganized matter are noticed to change
their forms, vary their light greatly, but not quickly; they change
through the ages. "God works slowly." He takes a thousand years
to lift his hand off.

[Illustration: Fig. 79.--Crab Nebula, near z Tauri. (See Frontispiece.)]

There are many unsolved problems connected with these strange bodies.
Whether they belong to our system, or are beyond it, is not settled;
the weight of evidence leans to the first view.

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_Variable Stars._

[Illustration: Fig. 80.--The Ring Nebula.]

Our sun gives a variable amount of light, changing through a period
of eleven years. Probably every star, if examined by methods
sufficiently delicate and exact, would be found to be var