Kepler, John, 59, 60, 63, 64, 65, 66, 70, 72, 73, 75, 77, 79, 84, 93, 94, 95, 104, 106, 107, 110, 122, 137, 145, 153, 158, 164, 165, 166, 167, 192, 200, 208, 209, 210, 211, 212, 214, 218, 224, 227, 253, 256, 259, 260, 262, 288, 295, 296, 332, 338, 361, 389; he replaced epicycles by an ellipse, 27; he was a pupil of Tycho Brahé, 54; he was a speculator more than an observer, 58; his personal life, 58, _seq._; his theories about the numbers and distances of the planets, 60, 62; he was helped by Tycho, 63; his main work, 65, _seq._; he gave up circular motion, 69; his _Mysterium Cosmographicon_, 105; his Laws, 71, 74, 173, 174, 176, 179, 180, 206, _seq._ L Lagrange, 193, 234, 255, 256, 257, 258, 263 Lagrange and Laplace, 258, 266, 395; they laid the foundations of the planetary theory, 259 Laplace, 68, 193, 218, 234, 255, 261, 262, 267, 268, 269, 270, 272, 288, 301, 317, 384, 385, 390; his nebular hypothesis, 267, 292; his _Mécanique Céleste_, 323 Lassell, Mr., 283, 284 Leibnitz, 192, 197, 233 Le Monnier, 319 Leonardo, see Vinci, Leonardo da Leverrier, 193, 327, 328, 329, 330, 352 Lippershey, Hans, 95 M Maskelyne, 281 Maxwell, Clerk, 302, 303 Molyneux, 248, 249 Morton, Mr. E.J. C, his Life of Copernicus, 31 N Newton, Prof. H.A., 347 Newton, Sir Isaac, 7, 30, 79, 138, 139, 144, 145, 149, 153, 157, 158, 165, 166, 167, 174, 176, 184, 187, 188, 189, 191, 192, 194, 196, 198, 199, 201, 213, 216, 219, 220, 221, 224, 226, 227, 228, 233, 242, 253, 255, 256, 274, 288, 317, 340, 378; his _Principia_, 191, 192, 193, 194, 195, 196, 197, 207, 214, 216, 218, 228, 233, 242, 253; his early life, 161, _seq._; his first experiments, 163; his work at Cambridge, 164; his Laws, 168; his application of the Laws of Gravity to Astronomy, 177, 178, 179, 185, 190; his reticence, 178; his discoveries in Optics, 181, _seq._; his work summarised, 186; his _Optics_, 189; anecdotes of him, 191; his appearance in a Court of Justice, 195; some of his manuscripts very recently discovered, 217; his theories of the Equinoxes and tides, 223, _seq._, 225, 363, _seq._ O Olbers, 299, 300 P Peters, Prof., 300, 316 Piazzi, 298, 299, 308, 313 Picard, 190, 242, 244, 247 Pioneers, genuine, 7 Planets and days of the week, 18 Poynting, 332 Printing, 9 Ptolemy, 18, 20, 27, 38, 153, 155, 166, 214; his system of the Heavens simplified by Copernicus, 11, 30; his system described, 19, _seq._; his system taught, 34; his harmonies, 74 Pythagoras, 19, 20, 34 Q Quadrant, an early, 42, 43 R Rheiter, 107 Ricci, Ostillio, 86, 87 Roberts, Isaac, 268 Roemer, 239, 240, 242, 244, 249, 251, 308 Rosse, Lord, his telescope, 186, 268 Rudolphine tables, 65 S Scheiner, 107 Sizzi, Francesca, an orthodox astronomer, 106 Snell, Willebrod, and the law of refraction, 65 Solar system, its fate, 265 Stars, a list of, 307 Struve, 308, 310, 311, 313 Stuart, Prof., quoted, 52 T Tatius, 296