On the key to the chart the Greek-letter names of the principal stars have been attached, but some of them have other names which are more picturesque. These are as follows: In Ursa Major (the Great Bear, which includes the Great Dipper), α is called Dubhe, β Merak, γ Phaed, δ Megrez, ε Alioth, ζ Mizar, and η Benetnash. The little star close by Mizar is Alcor. In Cassiopeia, α is called Schedar, β Caph, and δ Ruchbar. In Ursa Minor, the Little Bear, α is called Polaris, or the North Star, and β Kochab. In Draco, α is called Thuban, and γ Eltanin. In Cepheus, α is called Alderamin, and β Alfirk. These names are nearly all of Arabic origin. It will be observed that Merak and Dubhe are the famous “Pointers,” which serve to indicate the position of the North Star, while Thuban is the “star of the pyramid,” before mentioned. The north celestial pole is situated almost exactly on a straight line drawn from Mizar through the North Star to Ruchbar, and a little more than a degree from the North Star in the direction of Ruchbar. This furnishes a ready means for ascertaining the position of the meridian. For instance, about the middle of October, Mizar is very close to the meridian below the pole, and Ruchbar equally close to it above the pole, and then, since the North Star is in line with these two, it also must be practically on the meridian, and its direction indicates very nearly true north. The same method is applicable whenever, at any other time of the year or of the night, Mizar and Ruchbar are observed to lie upon a vertical line, no matter which is above and which below. It is also possible to make a very good guess at the time of night by knowing the varying position of the line joining these stars. The star Caph is an important landmark because it lies almost on the great circle of the equinoctial colure, which passes through the vernal and autumnal equinoxes. On the key, the location of the North Pole of the Ecliptic is shown, and the greater part of the circle described by the north celestial pole in the period of 25,800 years.