When Neptune was discovered he had just left the constellation Capricornus, and in the sixty-six years that his movements have been followed he has passed through Aquarius, Pisces, Aries, Taurus, and is now (1912) in Gemini, very near Castor and Pollux. The time required for his circuit around the sun is nearly one hundred and sixty-five (164.6) years, so that he remains for about thirteen years in each constellation. He will complete one sidereal period, dating from the time of his discovery, in the year 2011. The apparent motion of Neptune is direct a little more than six months in the year, and retrograde a little more than five months, so that it seems to present the old mental arithmetic problem of the climber that fell back so much every time after he had climbed a certain number of feet. But the falling back in the case of Neptune is an illusion, as we know. He keeps straight on in his journey, as we may see if we watch him from year to year, and his change of position is so slight during any year that the change of direction is hardly noticeable. Neptune is as bright as an eighth-magnitude star, and it is possible to see him with a good field-glass. The difficulty is in distinguishing him from a star, for his disc does not show except through a telescope. If one has such a glass, however, it will be worth while to direct it toward that part of the ecliptic just under Castor and Pollux any time within the next two or three years, and a sight of this yet strange brother planet may be the reward. He will be in opposition on January 14, 1913, and thereafter about two days later each year. XVII THE LITTLE PLANETS, OR THE ASTEROIDS The asteroids, or minor planets, are situated almost wholly in the vast space between Mars and Jupiter. Their orbits are very irregular, both as to shape and situation; but, so far as is known, only two of them pass beyond the orbit of Jupiter, and only one has been discovered which at any point in its journey around the sun comes nearer than the orbit of Mars. The minor planets are called by astronomers almost indifferently asteroids or planetoids. “Asteroids” is probably the name by which they are most popularly known. But because they are in fact simply little bodies that revolve about the sun as the planets do, “planetoids” seems to be more truly descriptive of them, and it is the word I have chosen to use here.