vi CONTENTS. 



CHAPTER IV. Miscellaneous Papers. 

 PART I. Experiments Bearing on the Properties of Coronas. 



PAGE 



47. Introductory. Figs. 44, 450, 456, 45^ Si 



48. Experiments with a grating. Table 12. Figs. 46, 47 82 



49. Experiments with small coronas 85 



50. Experiments with large coronas, annular source. Coronas by reflection. Figs. 



48, 49 86 



51 . Coronas from a point source. Figs. 50, 51 88 



PART II. Displacement Interferometry with Film Grating. 



52. Introductory. Figs. 52, 53 92 



53. Films between glass plates 92 



54. Continued. The groups i +4, i +5. Figs. 54, 55, 56, 57, 58, 59 93 



55. Continued. The groups 2 +4, 2 +5 94 



56. Continued. The groups 3+4. 3+5 95 



57. Centers of ellipses 95 



58. Film or ruling on one side of the glass plate. Ruled grating 96 



59. Continued. Film grating not cemented to glass. Fig. 60 97 



60. Single plate, film grating 97 



PART III. Elliptic Interferometry with a Nernst Filament. 



61. Introduction 98 



62. The Nernst burner. Fig. 61 99 



63. Remarks 99 



PART IV. Scattering in the Case of Regular Reflection from a Transparent Grating, 

 an Analogy to the Reflection of X-rays from Crystals. 



64. The phenomenon. Fig. 62 100 



65. Explanation 101 



66. A further analogy to the reflection of X-rays 102 



CHAPTER V. Displacement Interferometry Applied to the Quadrant Electrometer. 



67. Apparatus. Fig. 63 103 



68. Observations 104 



69. Observations, continued. Fig. 64 105 



70. Observations, continued. Figs. 6sA, 656 105 



71. Observations, continued 106 



72. Further observations. Table 13. Fig. 66 107 



73. Observations, continued. Tables 14, 15, 16, 17, 18 109 



74. Summary 112 



