Solar and Planetary Evolution. 67 



velopment beyond the condition of Jupiter. Millions of 

 years ago the earth was like Jupiter, and before that, it 

 was a sun, shining by its own light. Ages earlier still, it 

 was in the condition of a nebula. Now, we dwell on the 

 hardened surface of an extinguished star. The earth has 

 passed through all the stages of growth ; mountains, plains 

 and ocean-beds have been formed by gradual and entirely 

 natural processes ; and at last it has reached the stage in 

 which geological changes are so slow that the tiny coral 

 animals may be ranked among world-builders, as they lay 

 the foundations of future continents. Even in its present 

 condition, the earth is still radiating heat into space. Ac- 

 cording to Cfuyot, the earth at the time of the deposition 

 of the lower strata might be likened to a galvanic pile, 

 which radiated streams of electricity into surrounding space. 

 The earth retains the faint reflection of one of its solar 

 features in the auroral lights. These phenomena are of an 

 electrical character. The earth is a great magnet, having 

 its positive and negative poles, and it is near these poles 

 that the auroral lights shine the most brightly. There is 

 an intimate connection between the spots and outbursts 

 which we observe on the sun, and the magnetic condition 

 of the earth. 



When we contemplate this fair earth, with its manifold 

 beauties and teeming life, we naturally wish that this was 

 the last stage in its evolution ; but science will not let us 

 pause. The earth, astronomy tells us, must die, and be- 

 come like that dead world, the moon, which forever accom- 

 panies it, and shows what this world will sometime be. 

 The most bitter disappointment connected with the im- 

 provement of modern telescopes, is the discovery that the 

 moon is a dead world. (A magnified photograph of the 

 moon was shown. See Fig. 12, page 68.) It has vast ocean- 

 beds, but no water ; volcanoes, but no fire. There is no 

 grass, no clouds, no atmosphere. In all that dead world 

 there can be no sound ; for, without an atmosphere to con- 

 vey the waves of sound to the ear, though the beetling 

 crags of mountains should topple and fall there would be no 

 noise from the concussion. The moon as seen through the 

 telescope has a certain beauty, but it is the beauty of icicles, 

 not that of a living world. 



Light may be thrown upon the question of the formation 

 of the universe, by contemplating its shape or form. Her- 



