4 CONTENTS. 



CHAPTER VI. Channeled Spectra Occurring in Connection with the Diffraction of 



Reflecting Gratings. 



44. Introductory 95 



45. Apparatus. Fig. 70 95 



46. Scattering 95 



47. Fringes with white light 96 



48. Fringes with sodium light 97 



49. Grating on a spectrometer. Fig. 71 98 



50. Inferences 100 



CHAPTER VII. Prismatic Methods in Reversed and Non-reversed Spectrum 



Inlerferometry. 



51. Purpose 102 



52. Method and apparatus. Figs. 72, 73 102 



53. The same. Crossed rays 103 



54. Another method. Fig. 74 104 



55. Methods using prismatic dispersion. Fig. 75 105 



56. Methods with paired prisms. Fig. 76 106 



CHAPTER VIII. The Linear Type of Displacement Interferometers. 



57. Introductory 107 



58. Apparatus. Fig. 77 107 



59. Film grating. Adjustment. Figs. 78, 79 109 



60. Michelson's interferences no 



61. Film grating. Another adjustment. Fig. 80 in 



62. Equations 1 1 1 



CHAPTER IX. The Use of Compensators Bounded by Curved Surfaces. 



63. Introduction 113 



64. Lens systems 113 



65. Effective thickness of the lenticular compensator. Fig. 81 115 



66. Observations largely with weak lenses and short interferometer. Figs. 82, 83 1 16 



67. Remarks. Fig. 84 118 



68. Observation with lens systems on both sides. Figs. 85, 86 1 19 



69. Telescopic interferences. Figs. 87, 88, 89, 90, 91 120 



CHAPTER X. The Dispersion of Air. 



70. Introduction. Table 8 124 



71. Observations with arc lamp 124 



72. Observations with sunlight. Single tube. Table 9 125 



73. Two (differential) refraction tubes. Table 10. Fig. 92 127 



74. Differential and single refraction tubes. Sunlight. Tables n, 12 129 



75. Distortion of glass absent 131 



76. Further observations with sunlight. Table 13 131 



77. Conclusion I3 2 



CHAPTER XI. The Refraction of Air with Temperature. 



78. Apparatus. Fig. 93. Table 14 133 



79. Observations 134 



80. Computation 135 



81. Final experiments at 100. Table 15 136 



82. Experiments at red heat 137 



83. Further experiments at high temperatures. Fig. 94. Table 16 139 



84. Flames 140 



85. Conclusion I4. 1 



CHAPTER XII. Adiabatic Expansion Observed with the Interferometer. 



86. Introductory. Table 17 142 



87. Experiments with short, bulky air-chambers H3 



88. Effect of strained glass 145 



89. Equations *4-6 



90. Experiments with long tubes. Diameter, I inch. Table 18 148 



91. The same. Diameter of tube, 2 inches. Table 19 15 



92. The same. Diameter of tube, 4 inches. Tables 20, 21. Fig. 95 151 



CHAPTER XIII. Miscellaneous Experiments. 



93. Effect of ionization on the refraction of a gas 154 



94. Mach's interferences. Fig. 96 I 55 



95. A Rowland spectrometer for transmitting and reflecting gratings, plane or concave. 



Figs. 97, 98, 99 156 



