(a) While all the stars revolve in orbits and are moving through space at high speed, they are so far away from us that they seem to be fixed and for all practical purposes they may be considered to be fixed in their positions. (b) All the planets turn on their own axes and travel in orbits round the Sun. (3) _Point out and name 12 principal constellations._ (a) Twelve easy constellations are: (1) The Big Dipper; (2) The Little Dipper; (3) Cassiopeia; (4) Pegasus; (5) Orion; (6) Auriga and (7) Taurus, all of which are shown in Chapters I and II; (8) Gemini; (9) Leo; (10) Virgo; (11) The Scorpion, and (12) Sagittarius, which are constellations of the zodiac, and are shown in Chapter XI. (4) _Find the_ =North= _by means of other stars than the Pole Star_ (_which is the North Star_) _in case that star is obscured by clouds._ (a) This can be done by finding the constellation of Cassiopeia, see Chapter I; and also by Pegasus; Auriga and Orion, as explained in Chapter II. (5) _Have a general knowledge of the positions and movements of the Earth, Sun, Moon, and the Planets; and of tides, eclipses, meteors and comets._ (a) By reading the chapters on the Sun, Planets, Earth and Moon and (b) Other things in the sky carefully, you will be able to pass the requirements named in No. 5. (6) _Plot on at least two nights per month for six months the positions of all naked eye planets visible between sundown and one hour thereafter. The plot of each planet shall contain at least three fixed stars with their names or designations; colors of planets and stars are to be recorded as observed._ (a) How to plot the position of a planet is fully explained in the chapter on Planets, but you should also read the one on The Stars of the Zodiac, and have a good star map (App. O). APPENDIX B. =Figures.=--When explaining the positions and forms of things, it is often necessary to use certain terms and figures, that is to say, lines which are either real or imaginary, but which can be drawn on paper. See Fig. 185.