4 CONTENTS. 



CHAPTER IV. Refractivity Determined, Irrespective of Form, by Displacement Inter- 

 ferometry. 



PAGE. 



48. Introductory 95 



49. Preliminary experiments. Figs. 63, 64 95 



50. Apparatus 96 



51. Equations. Table 22 97 



52. Observations. Tables 23, 24. Figs. 65, 66 99 



53. Dispersion constants. Tables 25, 26. Fig. 67 100 



54. Further observations. Tables 27, 28. Figs. 68, 69 102 



55. Conclusion. Table 29 105 



CHAPTER V. Displacement Interferometry in Connection with U -Tubes. Jamin's 



Interferometer. 



56. Introduction. Figs. 70, 71, 72 107 



57. Apparatus. Michelson interferometer 107 



58. Equations 109 



59. Observations no 



60. Jamin's interferometer. Figs. 73, 74, 75, 76 in 



61. Vertical displacement of ellipses. Figs. 77, 78 114 



62. Displacement interferometer. Jamin type. Tables 30, 31, 32, 33. Fig. 79 .... 115 



63. Broad slit interferences. Achromatic fringes 120 



64. Wide slit. Homogeneous light. Sodium flame. Figs. 80, 81, 82, 83, 84, 85. ... 121 



65. Vertical displacement. Table 34. Fig. 86 126 



66. Angular displacement of fringes. Table 35. Fig. 87 128 



CHAPTER VI. The Displacement Interferometry of Small Angles and of Long Dis- 

 tances. Complementary Fringes. 



67. Parallel rays retracing their path. Figs. 88, 89, 90, 91, 92 130 



68. Groups of achromatic fringes. Table 36. Fig. 93 133 



69. Measurement of small angles without auxiliary mirror. Table 37 134 



70. Complementary fringes. Figs. 94, 95 135 



71. Equations 138 



72. Separated rigid vertical system. Figs. 96, 97 139 



73. The displacement interferometry of long distances 141 



74. Theory. Table 38 142 



