vi CONTENTS. 



mirrors. 12. Light reflected from the silvered surface. 13. 

 How a double image is produced. 14. Why one image is much 

 more faint than the other. 15. Positions in which the two 

 images are visible. 16. The image usually seen produced by the 

 posterior surface. 17. Effect of light absorbed by the glass. 

 18. Glasses rendered unfaithful in their tints. 19. A good 

 glass must have its surface parallel. 20. Defects of low-priced 

 glasses ' . . . -120 



THE TIDES. 



Their correspondence with the lunar phases known at an early 

 period. 2. Erroneous notions prevalent as to their causes. 3. 

 Not caused by the moon's attraction. 4. But by the inequality 

 of its attraction.- 5. Calculation of this inequality. 6. Solar 

 tides. 7. : Difference between the power of the sun and moon to 

 produce a tide.' 8. Spring and neap tides. 9. Why the tides 

 are not directly under the moon. 10. Establishment of the port. 

 11. Effects of the form of the coasts upon the local tides. 



12. Dr. Whewell's analysis of the progress of the tidal wave. 



13. Age of the tide. 14. Velocity of the tide. 15. Undulations. 

 - 16. Motion of the crest of a wave. 17. Bange of the tide. 

 18. How affected by the weather 



HOW TO OBSERVE THE HEAVENS. 



CHAP. I. 1. Spectacle presented by the firmament. 2. Useful ob- 

 servations can be made without astronomical instruments. 3. 

 Apparent motion of the firmament. 4. The meridian. 5. View 

 of* the circumpolar region. 6. Permanency of the form of the 

 stellar groups. 7. The celestial sphere. 8. The celestial poles. 

 9. Orders of magnitude of the stars. 10. Number of stars of 

 each order. 11. Constellations. 12. Ursa major. 13. Anti- 

 quity of the name. 14. Sometimes called Waggon, Wain, or 

 Chariot. 15. Number of stars in it. 16. Proper names of stars. 

 17. Use of the imaginary figure to express the position of the 

 stars. 18. Ursa minor : the pole star. 19. How it makes a 

 nocturnal clock. 20. Arctic circle : origin of the name. 21. 

 Cassiopeia's chair. 22. Pegasus and Andromeda. 23. Perseus. 

 24. Auriga. 25. General view of the region of these con- 

 stellations : Capella, Vega, Adrided, and Altair. 26. Orioni . 145 



CHAP. II. 27. Antiquity of the name of Orion. 28. Nebulae in the 

 constellation Orion. 29. General view of this region of the 

 heavens. 30. Procyon and Sirius. 31. Aldebaran : the Hyades 

 and the Pleiades. 32. The constellations of the zodiac. 33. Use 

 of celestial maps. 34. Use of a celestial globe. 35. To find the 

 place of an object in the heavens . . . . . .161 



