25. Double concave, plane concave, and concavo-convex lenses 61
26. Double convex, plane convex, and concavo-convex lenses 62
27. Convergence of rays by convex lens to principal focus 62
31. Dispersion of rays by a double concave lens 65
33. Action of eye in formation of images 68
35. Diagram showing path of rays when viewing an object at an 70 easy distance
39. Diagram explaining the magnifying power of object-glass 76
42. Diagram showing the amount of colour produced by a lens 81
43. Decomposition and recomposition of light by two prisms 83
44. Diagram explaining the formation of an achromatic lens 84
45. Combination of flint- and crown-glass lenses in an achromatic 86 lens
46. Diagram illustrating the irrationality of the spectrum 87
47. Diagram illustrating the action of a reflecting surface 91
48. Experimental proof that the angle of incidence = angle of 92 reflection
49. Convergence of light by concave mirror 94
51. Formation of image of candle by reflection 95
53. Reflection of rays by convex mirror 98
56. Reflecting telescope (Cassegrain) 103
58. Diagram illustrating spherical aberration 105
59. Diagram showing the proper form of reflector to be an ellipse 106
61. Diagram explaining the achromaticity of the Huyghenian 111 eyepiece
64. Images of planet produced by short and long focus lenses, &c. 123
65. Showing in an exaggerated form how the edge of the speculum 128 is worn down by polishing
65*. Section of Lord Rosse’s polishing machine 131
67. Simple telescope tube, showing arrangement of object-glass 140 and eyepiece
68. Appearance of diffraction rings round a star when the 141 object-glass is properly adjusted
69. Appearance of same object when object-glass is out of 141 adjustment
70. Optical part of a Newtonian reflector of ten inches aperture 143
71. Optical part of a Melbourne reflector 143
72. Mr. Browning’s method of supporting small specula 144
73. Support of the mirror when vertical 146
74. Division of the speculum into equal areas 147
75. Primary, secondary, and tertiary systems of levers shown 148 separately
76. Complete system consolidated into three screws 148
77. Support of diagonal plane mirror (Front view) 150
78. Support of diagonal plane mirror (Side view) 150
79. A portion of the constellation Gemini seen with the naked eye 154