Spica, the brightest star in Virgo, is a bluish-white, first-magnitude star, standing very much alone in the sky. In fact, the Arabs referred to this star as "The Solitary One." Its distance from the earth is not known, but must be very great as it cannot be found by the usual methods. The spectroscope shows that it consists of two suns very close together, revolving about a common center in a period of only four days. Within the branches of the "Y" in Virgo, and just to the north of it, is the wonderful nebulous region of this constellation, but it takes a powerful telescope to show the faint spiral nebulæ that exist here in great profusion. All of these spirals are receding from the plane of the Milky Way with enormous velocities. The spiral nebulæ are, in fact, the most rapidly moving objects in the heavens. VIII JULY Due east of the little circlet of stars known as Corona Borealis, and almost directly overhead in our latitude (40° N.) about nine o'clock in the evening in the early part of July, is the large constellation of Hercules, named for the famous hero of Grecian mythology. There are no stars of great brilliancy in this group, but it contains a large number of fairly bright stars arranged in the form outlined in the chart. The hero is standing with his head, marked by the star Alpha Herculis, toward the south, and his foot resting on the head of Draco, The Dragon, a far-northern constellation with which we become acquainted in August. [Illustration: JULY--HERCULES] Alpha Herculis, the best known star in this constellation, is of unusual interest. Not only is it a most beautiful double star, the brighter of the two stars of which it is composed being orange, and the fainter greenish-blue, but it is also a star that changes in brightness irregularly. Both the orange and the blue star share in this change of brightness. There are a number of stars in the heavens that vary in brightness, some in very regular periods, and others, like Alpha Herculis, irregularly. These latter stars are nearly always deep orange or reddish in color. One may note this variation in the brightness of Alpha Herculis by comparing it from time to time with some nearby star that does not vary in brightness. [Illustration: THE GREAT HERCULES CLUSTER--A UNIVERSE OF SUNS Taken with 60-inch Reflector of the Mt. Wilson Observatory]