Sweeping westward, we come upon Sigma 1669, a pretty little double with nearly equal components of about the sixth magnitude, distance 5.6", p. 124 deg.. But our interest is not fully aroused until we reach gamma, a star with a history. The components of this celebrated binary are both nearly of the third magnitude, distance about 5.8", p. 150 deg.. They revolve around their common center in something less than two hundred years. According to some authorities, the period is one hundred and seventy years, but it is not yet certainly ascertained. It was noticed about the beginning of the seventeenth century that gamma Virginis was double. In 1836 the stars were so close together that no telescope then in existence was able to separate them, although it is said that the disk into which they had merged was elongated at Pulkowa. In a few years they became easily separable once more. If the one-hundred-and-seventy-year period is correct, they should continue to get farther apart until about 1921. According to Asaph Hall, their greatest apparent distance is 6.3", and their least apparent distance 0.5"; consequently, they will never again close up beyond the separating power of existing telescopes. There is a great charm in watching this pair of stars even with a three-inch telescope--not so much on account of what is seen, although they are very beautiful, as on account of what we know they are doing. It is no slight thing to behold two distant stars obeying the law that makes a stone fall to the ground and compels the earth to swing round the sun.