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1. The Ptolemaic Idea of the Universe 19 2. The Copernican Theory of the Solar System 21 3. Total and Partial Eclipses of the Moon 64 4. Total and Partial Eclipses of the Sun 67 5. "Baily's Beads" 70 6. Map of the World on Mercator's Projection, showing a portion of the progress of the Total Solar Eclipse Of August 30, 1905, across the surface of the Earth 81 7. The "Ring with Wings" 87 8. The Various Types of Telescope 113 9. The Solar Spectrum 123 10. A Section through the Sun, showing how the Prominences rise from the Chromosphere 131 11. Orbit and Phases of an Inferior Planet 148 12. The "Black Drop" 153 13. Summer and Winter 176 14. Orbit and Phases of the Moon 184 15. The Rotation of the Moon on her Axis 187 16. Laplace's "Perennial Full Moon" 191 17. Illustrating the Author's explanation of the apparent Enlargement of Celestial Objects 195 18. Showing how the Tail of a Comet is directed away from the Sun 248 19. The Comet of 1066, as represented in the Bayeux Tapestry 263 20. Passage of the Earth through the thickest portion of a Meteor Swarm 269

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ASTRONOMY OF TO-DAY

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CHAPTER I

THE ANCIENT VIEW

It is never safe, as we know, to judge by appearances, and this is perhaps more true of astronomy than of anything else.

For instance, the idea which one would most naturally form of the earth and heaven is that the solid earth on which we live and move extends to a great distance in every direction, and that the heaven is an immense dome upon the inner surface of which the stars are fixed. Such must needs have been the idea of the universe held by men in the earliest times. In their view the earth was of paramount importance. The sun and moon were mere lamps for the day and for the night; and these, if not gods themselves, were at any rate under the charge of special deities, whose task it was to guide their motions across the vaulted sky.

Little by little, however, this simple estimate of nature began to be overturned. Difficult problems agitated the human mind. On what, for instance, did the solid earth rest, and what prevented the vaulted heaven from falling in upon men and crushing them out of existence? Fantastic myths sprang from the vain attempts to solve these riddles. The Hindoos, for example, imagined the earth as supported by four elephants which stood upon the back of a gigantic tortoise, which, in its turn, floated on the surface of an elemental ocean. The early Western civilisations conceived the fable of the Titan Atlas, who, as a punishment for revolt