CONTENTS. 



CHAPTER I. The Displacement Interferometry of Long Distances. 



PAGE. 



1 . Introduction 7 



2. Apparatus. Fig. i 7 



3. Rigorous equations. Figs. 2,3 8 



4. Ocular micrometer. Fig. 4 II 



5. Collimator micrometer. Fig. 5 15 



6. Half-silvered films 1 6 



7. Direct observations 18 



8. Indirect observations. Fig. 6 19 



9. Ellipses and hyperbolas 21 



10. Compensators. Figs. 7, 8 23 



1 1 . Number of fringes visible 25 



12. Separate adjustable auxiliary mirrors. Figs. 9, 10, n, 12 25 



13. Types of achromatic fringes 27 



CHAPTER II. The Interferometry of Small Angles. Methods by Direct and 



Reversed Superposed Spectra. 



14. Introductory 29 



15. Method with prism. Figs. 13, 14, 15 29 



16. Estimate 30 



17. Equations 31 



18. Observations. Prism-prism method. Fig. 16 34 



19. Interference from rough surfaces. Figs. 17,18 36 



20. Reversed rays. Figs. 19, 20, 21 37 



2 1 . Second method. Figs. 22, 23 40 



22. Equations 41 



23. Observations. Figs 24, 25 43 



24 . Reversed rays 46 



25. Fringes from rough surfaces 48 



26. Direct interferences without cleavage prism. Fig. 26 49 



CHAPTER III. The Elastics of Small Bodies. 



27. Introductory method. Fig. 27 53 



28. Apparatus. Figs. 28, 29, 30 54 



29. Preliminary observations. Figs. 31, 32, 33 55 



30. Rods in metallic sheath. Figs. 34, 35, 36, 37, 38, 39 59 



31. The same. Thinner rods, hard rubber. Figs. 40, 41, 42, 43 59 



32. The same. Brass 61 



33. The same. Glass. Fig. 44 63 



34. The same. Steel 64 



35. Modifications of apparatus. Figs. 45, 46 64 



36. Observations. Figs. 47, 48, 49 65 



37. Apparent yield within the apparatus 66 



38. Ocular micrometer. Collimator micrometer 68 



39. Summary. Figs. 50, 51 . . 69 



CHAPTER IV. Experiments in Gravitation. 



I. GRAVITATIONAL ATTRACTION. 



40. Introduction 73 



41. Equations 73 



42. Observations. Floating system. Figs. 52, 53 74 



43. Expeditious fringe detection 75 



44. Heavy needle in air 76 



45. Light needle in air. Figs. 54, 55, 56 76 



46. Summer experiments 79 



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