Does the Number of Aerolitic Falls vary with the Earth's Distance from the Sun?--Relative Numbers observed in the Forenoon and Afternoon--Extent of the Atmosphere as indicated by Meteors 79 CHAPTER IX. The Meteoric Theory of Solar Heat 84 CHAPTER X. Will the Meteoric Theory account for the Phenomena of Variable and Temporary Stars? 92 CHAPTER XI. The Lunar and Solar Theories of the Origin of Aerolites 96 CHAPTER XII. The Rings of Saturn 102 CHAPTER XIII. The Asteroid Ring between Mars and Jupiter 105 CHAPTER XIV. Origin of Meteors--The Nebular Hypothesis 112 APPENDIX 123 INTRODUCTION. A GENERAL VIEW OF THE SOLAR SYSTEM. THE SOLAR SYSTEM consists of the sun, together with the planets and comets which revolve around him as the center of their motions. The sun is the great controlling orb of this system, and the source of light and heat to its various members. Its magnitude is one million four hundred thousand times greater than that of the earth, and it contains more than seven hundred times as much matter as all the planets put together. MERCURY is the nearest planet to the sun; its mean distance being about thirty-seven millions of miles. Its diameter is about three thousand miles, and it completes its orbital revolution in 88 days. VENUS, the next member of the system, is sometimes our morning and sometimes our evening star. Its magnitude is almost exactly the same as that of the earth. It revolves round the sun in 225 days. THE EARTH is the third planet from the sun in the order of distance; the radius of its orbit being about ninety-five millions of miles. It is attended by one satellite--the moon--the diameter of which is 2160 miles. MARS is the first planet exterior to the earth's orbit. It is considerably smaller than the earth, and has no satellite. It revolves round the sun in 687 days. THE ASTEROIDS.--Since the commencement of the present century a remarkable zone of telescopic planets has been discovered immediately exterior to the orbit of Mars. These bodies are extremely small; some of them probably containing less matter than the largest mountains on the earth's surface. More than ninety members of the group are known at present, and the number is annually increasing. JUPITER, the first planet exterior to the asteroids, is nearly five hundred millions of miles from the sun, and revolves round him in a little less than twelve years. This planet is ninety thousand miles in diameter and contains more than twice as much matter as all the other planets, primary and secondary, put together. Jupiter is attended by four moons or satellites.