Next east of Virgo is Libra, which contains a few notable objects (map No. 10). The star alpha has a fifth-magnitude companion, distant about 230", which can be easily seen with an opera glass. At the point marked A on the map is a curious multiple star, sometimes referred to by its number in Piazzi's catalogues as follows: 212 P. xiv. The two principal stars are easily seen, their magnitudes being six and seven and a half; distance 15", p. 290 deg.. Burnham found four other faint companions, for which it would be useless for us to look. The remarkable thing is that these faint stars, the nearest of which is distant about 50" from the largest member of the group and the farthest about 129", do not share, according to their discoverer, in the rapid proper motion of the two main stars. In iota we find a double a little difficult for our three-inch. The components are of magnitudes four and a half and nine, distance 57", p. 110 deg.. Burnham discovered that the ninth-magnitude star consists of two of the tenth less than 2" apart, p. 24 deg.. No astronomer who happens to be engaged in this part of the sky ever fails, unless his attention is absorbed by something of special interest, to glance at beta Librae, which is famous as the only naked-eye star having a decided green color. The hue is pale, but manifest.[3] [3] Is the slight green tint perceptible in Sirius variable? I am sometimes disposed to think it is. The star is a remarkable variable, belonging to what is called the Algol type. Its period, according to Chandler, is 2 days 7 hours, 51 minutes, 22.8 seconds. The time occupied by the actual changes is about twelve hours. At maximum the star is of magnitude five and at minimum of magnitude 6.2. [Illustration: MAP NO. 11.] We may now conveniently turn northward from Virgo in order to explore Booetes, one of the most interesting of the constellations (map No. 11). Its leading star alpha, Arcturus, is the brightest in the northern hemisphere. Its precedence over its rivals Vega and Capella, long in dispute, has been settled by the Harvard photometry. You notice that the color of Arcturus, when it has not risen far above the horizon, is a yellowish red, but when the star is near mid-heaven the color fades to light yellow. The hue is possibly variable, for it is recorded that in 1852 Arcturus appeared to have nearly lost its color. If it should eventually turn white, the fact would have an important bearing upon the question whether Sirius was, as alleged, once a red or flame-colored star.