ct idea will be conveyed by the last figure of
Plate 3. This nebula was discovered in 1772, by Darquier, at Toulouse.
It is seen as a ring of light with very moderate telescopic power. In a
good 3-1/2-inch telescope the nebula exhibits a mottled appearance and a
sparkling light. Larger instruments exhibit a faint light within the
ring; and in Lord Rosse's great Telescope "wisps of stars" are seen
within, and faint streaks of light stream from the outer border of the
ring. This nebula has been subjected to spectrum-analysis by Mr.
Huggins. It turns out to be a gaseous nebula! In fact, ring-nebulae--of
which only seven have been detected--seem to belong to the same class as
the planetary nebulae, all of which exhibit the line-spectrum indicative
of gaseity. The brightest of the three lines seen in the spectrum of the
ring-nebula in Lyra presents a rather peculiar appearance, "since it
consists," says Mr. Huggins, "of two bright dots, corresponding to
sections of the ring, and between these there is not darkness, but an
excessively faint line joining them. This observation makes it probable
that the faint nebulous matter occupying the central portion is similar
in constitution to that of the ring."

The constellation Hercules also contains many very interesting objects.
Let us first inspect a nebula presenting a remarkable contrast with that
just described. I refer to the nebula 13 M, known as Halley's nebula
(Plate 3). This nebula is visible to the naked eye, and in a good
telescope it is a most wonderful object: "perhaps no one ever saw it for
the first time without uttering a shout of wonder." It requires a very
powerful telescope completely to resolve this fine nebula, but the
outlying streamers may be resolved with a good 3-inch telescope. Sir W.
Herschel considered that the number of the stars composing this
wonderful object was at least 14,000. The accepted views respecting
nebulae would place this and other clusters far beyond the limits of our
sidereal system, and would make the component stars not very unequal (on
the average) to our own sun. It seems to me far more probable, on the
contrary, that the cluster belongs to our own system, and that its
components are very much smaller than the average of separate stars.
Perhaps the whole mass of the cluster does not exceed that of an average
first-magnitude star.

The nebulae 92 M and 50 H may be found, after a little searching, from
the positions indicated in the m