The third planet from the sun is our earth, ninety-two million miles from the source of its light and heat. Circling around the earth, and moving with it in its orbit, goes the moon. The earth rotates on its axis once in about twenty-four hours, giving us day and night in that period of time, according as, during its revolution, a part of the surface is turned to or from the sun. As the earth rolls over upon itself, it also rolls along its orbit, or sky-path. The path of the earth about the sun is travelled over in three hundred and sixty-five and a quarter days, giving us our change of seasons by the inclination of the earth’s axis to the plane of its orbit. Next removed beyond the earth from the sun, is the splendid planet Mars, which is easily distinguishable by its red light. It is in some parts of its path only seven millions of miles further from the earth than Venus. Mars has a day of about the same length as ours, and its seasons are of nearly the same intensity; but while a season is three months long with us, on Mars it is very nearly six months, for Mars takes almost two of our years to travel round the sun. Mars has a snow or ice-cap at each pole; it has also an atmosphere, as with a telescope we can observe clouds drifting across its sky, the clouds being formed as clouds here, by the evaporation of water from the surface of the globe, which moisture, being carried up in invisible vapor, is condensed by colder currents of air and forms clouds. The red light of Mars is supposed to be produced by the color of its surface, and by some it is considered that the vegetation on Mars may be red, as ours is green, and that to an observer on Mars, our planet would shine with a green light, as to us Mars shines in red. The poles of Mars are always white. Next after the moon Mars is the planet best known to us, because sometimes, as our globe and Mars pursue their paths through space, they come upon the same side of their path at the same time, which shortens the distance between them, and enables close observations to be taken. Between Mars and the next planet Jupiter there is a very great space, so great that astronomers considered that it could not be empty, but must have in it planets too small for easy observation. They therefore resolved to search that part of the sky constantly and carefully with telescopes. On the first day of this century a small planet was seen in this space, and was named Ceres. This was the first-found asteroid. From their small size these planets are called asteroids or starlets. Others were found, slowly at first, and then more and more; in April, 1891, the 309th was discovered by Dr. Palisa.