(the Twins), the third constellation in the zodiac. It is referred by the Greeks not only to the fable of Castor and Pollux, but also to those of Hercules and Apollo, Triptolemus and Iasion, Amphion and Zethus, &c. The constellation derives its name from two remarkable stars to which the names Castor (or α Gemini) and Pollux (or β Gemini) are given. These two stars may be easily found by drawing a straight line through the belt of Orion and the two bright stars the line of which cuts through the belt. This line protracted upwards very nearly passes through the two stars of Gemini. They may also be recognised by being about midway between Aldebaran and Regulus; and should Orion and Ursa Major be seen at the same time, then Castor and Pollux on the one side, and Capella on the other, are conspicuous boundaries of the intermediate space. On Jan. 1, 1856, the right ascension of Castor was 7h 25m 24s.357, with an annual variation of +3°54.33; and his declination was 32° 11' 58".73 N., with an annual variation of −7°.38. On the same day the right ascension of Pollux was 7h 36m 29s.907, with an annual variation of +3°68.22; and his declination was 28° 22' 11".59 N., with an annual variation of −8°.258. Their respective magnitudes were 2.1 and 1.2.