By GARRETT P. SERVISS.
IV. — VIRGO AND HER NEIGHBORS.
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 α, a yellow fourth-magnitude star, near which is a celebrated red variable R. With a low power we can see both a 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 α. 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 α is very pleasing.
There is hardly anything else in Crater to interest us, and we pass over the border into Corvus, and go at once to its chief attraction, the star 8. The components of this beautiful double are of magnitudes three and eight; distance 24", p. 211°; colors yellow and purple.
The night being dark and clear, we take the five-inch and turn it on the nebula 3128, which the map shows just under the border of Corvus in the edge of Hydra. Herschel believed he had resolved this into stars. It is a faint object and small, not exceeding one eighth of the moon's diameter.
Further east in Hydra, as indicated near the left-hand edge of map No. 8, is a somewhat remarkable variable, R Hydræ. This star occasionally reaches magnitude three and a half, while at minimum it is not much above the tenth magnitude. Its period is about four hundred and twenty-five days.
While we have been examining these comparatively barren regions, glad to find one or two colored doubles to relieve the monotony of the search, a glittering white star has frequently drawn our eyes eastward and upward. It is Spica, the great gem of Virgo, and, yielding to its attraction, we now enter the richer constellation over which it presides (map No. 9). Except for its beauty, which every one must admire, Spica, or α Virginis, has no special claim upon our attention. Some evidence has been obtained that, like β Aurigæ, it revolves with an invisible com-