58. } { 171 59. } DIAGRAMS ILLUSTRATIVE OF THOSE NEAR THE BEGINNING { 174 60. } OF NEWTON'S "PRINCIPIA" { 175 61-2. } { 175 63. PRISMATIC DISPERSION 182 64. A SINGLE CONSTITUENT OF WHITE LIGHT IS CAPABLE OF NO MORE DISPERSION 183 65. PARALLEL BEAM PASSING THROUGH A LENS 184 66. NEWTON'S TELESCOPE 186 67. THE SEXTANT, AS NOW MADE 187 68. NEWTON WHEN YOUNG 196 69. SIR ISAAC NEWTON 200 70. ANOTHER "PRINCIPIA" DIAGRAM 207 71. WELL-KNOWN MODEL EXHIBITING THE OBLATE SPHEROIDAL FORM AS A CONSEQUENCE OF SPINNING ABOUT A CENTRAL AXIS 219 72. JUPITER 221 73. DIAGRAM OF EYE LOOKING AT A LIGHT REFLECTED IN A DISTANT MIRROR THROUGH THE TEETH OF A REVOLVING WHEEL 238 74. FIZEAU'S WHEEL, SHOWING THE APPEARANCE OF DISTANT IMAGE SEEN THROUGH ITS TEETH 239 75. ECLIPSES OF ONE OF JUPITER'S SATELLITES 241 76. A TRANSIT INSTRUMENT FOR THE BRITISH ASTRONOMICAL EXPEDITION, 1874 243 77. DIAGRAM OF EQUATORIALLY MOUNTED TELESCOPE 245 78. ABERRATION DIAGRAM 250 79. SHOWING THE THREE CONJUNCTION PLACES IN THE ORBITS OF JUPITER AND SATURN 259 80. LORD ROSSE'S DRAWING OF THE SPIRAL NEBULA IN CANES VENATICI 269 81. SATURN 271 82. PRINCIPLE OF NEWTONIAN REFLECTOR 278 83. HERSCHEL'S 40-FOOT TELESCOPE 283 84. WILLIAM HERSCHEL 285 85. CAROLINE HERSCHEL 287 86. DOUBLE STARS 288 87. OLD DRAWING OF THE CLUSTER IN HERCULES 290 88. OLD DRAWING OF THE ANDROMEDA NEBULA 291 89. THE GREAT NEBULA IN ORION 292 90. PLANETARY ORBITS TO SCALE 297 91. DIAGRAM ILLUSTRATING PARALLAX 307