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CONTENTS. 



COMMON THINGS CLOCKS AND WATCHES. 



PAGE 



CHAP. I. 1. General want of time measurers. 2. No natural 

 measures for short intervals. 3. Approximative expedient by 

 shadows. 4. Sun-dials. 5. Differently constructed for different 

 places. 6. Earliest sun-dials. 7. Clepsydra, or water-clock. 

 8. Hour-glass. 9. Mercurial time-gauge. 10. Clocks their 

 chief parts. 11. Regulating power of the pendulum. 12. 'Uni- 

 form rate of vibration. 13. Analysis of a vibration. 14. 

 Experimental verification of isochronism. 15. Moving power 

 sustains the vibration. 16. Vibration not dependent on weight 

 of pendulum. 17. Time of vibration varies with the length. 

 18. Analysis of motion of pendulous mass. 19. How the pen- 

 dulum governs the hands. 20. Produces intermitting motion. 

 21. Pendulum's motion maintained by moving power 



CHAP. II. 22. Action of pendulum on escapement wheel. 23. Rate 

 of motion of hands produced by tooth and pinion work. 

 24. Method of making pinions. 25. Mutual action of toothed 

 wheels. 26. Wheel and pinion. 27. Bevelled and crown 

 wheels. 28. Weight applied as a moving power. 29. Why 

 hands not turned back when clock is wound up. 30. Main- 

 spring. 31. Its power variable. 32. The fusee. 33. Balance- 

 wheel. 34. Its vibrations uniform. 35. General explanation 

 of a watch. 36. Of a clock moved by a weight. 37. Method 

 of regulating the rate 17 



CHAP. III. 38. Method of regulating a balance-wheel. 39. Recoil 

 escapement. 40. Cylindrical escapement. 41. Duplex. 

 42. Lever. 43. Detached. 44. Maintaining power of a clock 

 moved by a weight. 45. Of a watch moved by a main- 

 spring. 46. Weight of mainspring and pendulum and balance- 

 wheel variously combined. 47. Watches and chronometers. 

 48. Marine chronometers. 49. Stationary chronometers. 50. 

 Striking apparatus. 33 



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