n the central portion of Hydra, represented on
map No. 7, we find its leading star alpha, sometimes called Alphard, or
Cor Hydrae, a bright second-magnitude star that has been suspected of
variability. It has a decided orange tint, and is accompanied, at a
distance of 281", p. 153 deg., by a greenish tenth-magnitude star. Bu. 339
is a fine double, magnitudes eight and nine and a half, distance 1.3",
p. 216 deg.. The planetary nebula 2102 is about 1' in diameter, pale blue in
color, and worth looking at, because it is brighter than most objects of
its class. Tempel and Secchi have given wonderful descriptions of it,
both finding multitudes of stars intermingled with nebulous matter.

For a last glimpse at celestial splendors for the night, let us turn to
the rich cluster 1630, in Argo, just above the place where the stream of
the Milky Way--here bright in mid-channel and shallowing toward the
shores--separates into two or three currents before disappearing behind
the horizon. It is by no means as brilliant as some of the star clusters
we have seen, but it gains in beauty and impressiveness from the
presence of one bright star that seems to captain a host of inferior
luminaries.

CHAPTER IV

VIRGO AND HER NEIGHBORS

... "that region
Where still by night is seen
The Virgin goddess near to bright Booetes."--POSTE'S ARATUS.

[Illustration: MAP NO. 8.]

Following the order of right ascension, we come next to the little
constellations Crater and Corvus, which may be described as standing on
the curves of Hydra (map No. 8). Beginning with Crater, let us look
first at alpha, a yellow fourth-magnitude star, near which is a
celebrated red variable R. With a low power we can see both alpha and R
in the same field of view, like a very wide double. There is a third
star of ninth magnitude, and bluish in color, near R on the side toward
alpha. R is variable both in color and light. When reddest, it has been
described as "scarlet," "crimson," and "blood-colored"; when palest, it
is a deep orange-red. Its light variation has a period the precise
length of which is not yet known. The cycle of change is included
between the eighth and ninth magnitudes.

While our three-inch telescope suffices to show R, it is better to use
the five-inch, because of the faintness of the star. When the color is
well seen, the contrast with alpha is very pleasing.

There is hardly anything else in Crater to interest us,