To put it in another way: Jupiter, at the distance of the nearest stars, would be not far from one hundred times less bright than the faintest star which the largest telescope is just able, under the most exquisite conditions, to glimpse. To see a star so faint as that would require an object-glass of a diameter half as great as the length of the tube of the Lick telescope, or say thirty feet!

Of course, Jupiter might be more brilliantly illuminated by a brighter star than the sun; but, granting that, it still would not be visible at such a distance, even if we neglect the well-known concealing or blinding effect of the rays of a bright star when the observer is trying to view a faint one close to it. Clearly, then, the obscure objects seen by Dr. See near some of the stars, if they really are bodies visible only by light reflected from their surfaces, must be enormously larger than the planet Jupiter, and can not, accordingly, be admitted into the category of planets proper, whatever else they may be.

Perhaps they are extreme cases of what we see in the system of Sirius—i.e., a brilliant star with a companion which has ceased to shine as a star while retaining its bulk. Such bodies may be called planets in that they only shine by reflected light, and that they are attached to a brilliant sun; but the part that they play in their systems is not strictly planetary. Owing to their great mass they bear such sway over their shining companions as none of our planets, nor all of them combined, can exercise; and for the same reason they can not, except in a dream, be imagined to possess that which, in our eyes, must always be the capital feature of a planet, rendering it in the highest degree interesting wherever it may be found—sentient life.

It does not follow, however, that there are no real planetary bodies revolving around the stars. As Dr. See himself remarks, such insignificant bodies as our planets could not be seen at the distance of the fixed stars, "even if the power of our telescopes were increased a hundredfold, and consequently no such systems are known."

This brings me to another branch of the subject. In the same article from which I have already quoted (Recent Discoveries respecting the Origin of the Universe, Atlantic Monthly, vol. lxxx, pages 484-492), Dr. See sets forth the main results of his well-known studies on the origin of the double and multiple star systems. He finds that the stellar systems differ from the solar system markedly in two respects, which he thus describes:

"1. The orbits are highly eccentric; on the average twelve times more elongated than those of the planets and satellites.

"2. The components of the stellar systems are frequently equal and always comparable in mass, whereas our satellites are insignificant compared to their planets, and the planets are equally small compared to the sun."

These peculiarities of the star systems Dr. See ascribes to the effect of "tidal friction," the double stars having had their birth through fission of original fluid masses (just as the moon, according to George Darwin's theory, was born from the earth), and the reaction of tidal friction having not only driven them gradually farther apart but rendered their orbits more and more eccentric. This manner of evolution of a stellar system Dr. See contrasts with Laplace's hypothesis of the origin of the planetary system through the successive separation of rings from the periphery of the contracting solar nebula, and the gradual breaking up of those rings and their aggregation into spherical masses or planets. While not denying that the process imagined by Laplace may have taken place in our system, he discovers no evidence of its occurrence among the double stars, and this leads him to the following statement, in which believers in the old theological doctrine that the earth is the sole center of mortal life and of divine care would have found much comfort:

"It is very singular that no visible system yet discerned has any resemblance to the orderly and beautiful system in which we live; and one is thus led to think that probably our system is unique in its character. At least it is unique among all known systems."

If we grant that the solar system is the only one in which small planets exist revolving around their sun in nearly circular orbits, then indeed we seem to have closed all the outer universe against such beings as the inhabitants of the earth. Beyond the sun's domain only whirling stars, coupled in eccentric orbits, dark stars, some of them, but no planets—in short a wilderness, full of all energies except those of sentient life! This is not a pleasing picture, and I do not think we are driven to contemplate it. Beyond doubt, Dr. See is right in concluding that double and multiple star systems, with their components all of magnitudes comparable among themselves, revolving in exceedingly eccentric orbits under the stress of mutual gravitation, bear no resemblance to the orderly system of our sun with its attendant worlds. And it is not easy to imagine that the respective members of such systems could themselves be the centers of minor systems of planets, on account of the perturbing influences to which the orbits of such minor systems would be subjected.

But the double and multiple stars, numerous though they be, are outnumbered a hundred to one by the single stars which shine alone as our sun does. What reason can we have, then, for excluding these single stars, constituting as they do the vast majority of the celestial host, from a similarity to the sun in respect to the manner of their evolution from the original nebulous condition? These stars exhibit no companions, such planetary attendants as they may have lying, on account of their minuteness, far beyond the reach of our most powerful instruments. But since they vastly outnumber the binary and multiple systems, and since they resemble the sun in having no large attendants, should we be justified, after all, in regarding our system as "unique"? It is true we do not know, by visual evidence, that the single stars have planets, but we find planets attending the only representative of that class of stars that we are able to approach closely—the sun—and we know that the existence of those planets is no mere accident, but the result of the operation of physical laws which must hold good in every instance of nebular condensation.

Two different methods are presented in which a rotating and contracting nebula may shape itself into a stellar or planetary system. The first is that described by Laplace, and generally accepted as the probable manner of origin of the solar system—viz., the separation of rings from the condensing mass, and the subsequent transformation of the rings into planets. The planet Saturn is frequently referred to as an instance of the operation of this law, in which the evolution has been arrested after the separation of the rings, the latter having retained the ring form instead of breaking and collecting into globes, forming in this case rings of meteorites, and reminding us of the comparatively scattered rings of asteroids surrounding the sun between the orbits of Mars and Jupiter. This Laplacean process Dr. See regards as theoretically possible, but apparently he thinks that if it took place it was confined to our system.

The other method is that of the separation of the original rotating mass into two nearly equal parts. The mechanical possibility of such a process has been proved, mathematically, by Poincare and Darwin. This, Dr. See thinks, is the method which has prevailed among the stars, and prevailed to such a degree as to make the solar system, formed by the ring method, probably a unique phenomenon in the universe.

Is it not more probable that both methods have been in operation, and that, in fact, the ring method has operated more frequently than the other? If not, why do the single stars so enormously outnumber the double ones? It is of the essence of the fission process that the resulting masses should be comparable in size. If, then, that process has prevailed in the stellar universe to the practical exclusion of the other, there should be very few single stars; whereas, as a matter of fact, the immense majority of the stars are single. And, remembering that the sun viewed from stellar distances would appear unattended by subsidiary bodies, are we not justified in concluding that its origin is a type of the origin of the other single stars?

While it is, as I have remarked, of the essence of the fission process that the resulting parts of the divided mass should be comparable in magnitude, it is equally of the essence of the ring, or Laplacean process, that the bodies separated from the original mass should be comparatively insignificant in magnitude.

As to the coexistence of the two processes, we have, perhaps, an example in the solar system itself. Darwin's demonstration of the possible birth of the moon from the earth, through fission and tidal friction, does not apply to the satellites attending the other planets. The moon is relatively a large body, comparable in that respect with the earth, while the satellites of Jupiter and Saturn, for instance, are relatively small. But in the case of Saturn there is visible evidence that the ring process of satellite formation has prevailed. The existing rings have not broken up, but their very existence is a testimony of the origin of the satellites exterior to them from other rings which did break up. Thus we need not go as far away as the stars in order to find instances illustrating both the methods of nebular evolution that we have been dealing with.

The conclusion, then, seems to be that we are not justified in assuming that the solar system is unique simply because it differs widely from the double and multiple star systems; and that we should rather regard it as probable that the vast multitude of stars which do not appear, when viewed with the telescope, or studied by spectroscopic methods, to have any attendants comparable with themselves in magnitude, have originated in a manner resembling that of the sun's origin, and may be the centers of true planetary systems like ours. The argument, I think, goes further than to show the mere possibility of the existence of such planetary systems surrounding the single stars. If those stars did not originate in a manner quite unlike the origin of the sun, then the existence of planets in their neighborhood is almost a foregone conclusion, for the sun could hardly have passed through the process of formation out of a rotating nebula without evolving planets during its contraction. And so, notwithstanding the eccentricities of the double stars, we may still cherish the belief that there are eyes to see and minds to think out in celestial space.



INDEX

NOTE.—Double, triple, multiple, and colored stars, star clusters, nebulae, and temporary stars will be found arranged under the heads of their respective constellations.

ANDROMEDA, Map No. 24, 125. Stars: alpha, 126. gamma, 128. , 126. 36, 128. Temporary star: 1885, 127. Cluster: 457, 128. Variable: R, 128. Nebula: 116, 126.

AQUARIUS, Map No. 18, 107. Stars: zeta, 106. tau, 108. psi, 108. 41, 106. Sigma 2729, 106. Sigma 2745 (12), 106. Sigma 2998, 108. Variables: R, 108. S, 108. T, 106. Nebulae: 4628 (Rosse's "Saturn"), 108. 4678, 108.

AQUILA, Map No. 16, 95. Stars: pi, 94. 11, 94. 23, 94. 57, 94. Sigma 2644, 94. Sigma 2544, 94. Cluster: 4440, 94. Variables: eta, 94. R, 94.

ARGO: Map No. 2, 31; Map No. 7, 55. Stars: Sigma 1097, 33. Sigma 1146 (5), 35. Clusters: 1551, 35. 1564, 35. 1571, 35. 1630, 56. Nebula: 1564, 35.

ARIES, Map No. 22, 119. Stars: gamma, 118. epsilon, 120. lambda, 118. pi, 118. 14, 118. 30, 118. 41, 118. 52, 120. Sigma 289, 118.

AURIGA, Map No. 5, 45. Stars: alpha (Capella), 44. beta (Menkalina), 46. epsilon, 50. theta, 48. lambda, 50. 14, 50. 26, 50. 41, 51. Sigma 616, 48. Temporary star: 1892, 48. Clusters: 996, 51. 1067, 51. 1119, 51. 1166, 51. 1295, 48.

BOOeTES, Map No. 11, 67. Stars: alpha (Arcturus), 66. delta, 71. epsilon (Mirac), 71. zeta, 70. iota, 71. kappa, 71. , 71. xi, 70. pi, 70. Sigma 1772, 70. Sigma 1890 (39), 71. Sigma 1909 (44), 71. Sigma 1910 (279), 70. Sigma 1926, 71.

CAMELOPARDALUS, Map No. 25, 133. Stars: 1, 134. 2, 134. 7, 135. Sigma 385, 134. Sigma 390, 134. Cluster: 940, 135.

CANES VENATICI, Map No. 26, 137; Map No. 11, 67. Stars: 2, 136. 12 (Cor Caroli), 136. Sigma 1606, 136. Sigma 1768 (25), 72. Cluster: 3936, 72. Nebula: 3572, 136.

CANIS MAJOR, Map No. 2, 31. Stars: alpha (Sirius), 30. delta, 33. , 33. Clusters: 1454, 33. 1479, 33. 1512, 33. Variable: gamma, 33. Nebula: 1511, 33.

CANIS MINOR, Map No. 3, 34. Stars: alpha (Procyon), 36. 14, 36. Sigma 1126 (31 Can. Min. Bode), 36.

CANCER, Map No. 4, 39. Stars: zeta, 43. iota, 44. 66, 44. Sigma 1223, 44. Sigma 1291, 44. Sigma 1311, 44. Clusters: Praesepe, 43. 1712, 44.

CAPRICORNUS, Map No. 13, 83; Map No. 18, 107. Stars: alpha, 84. beta, 85. omicron, 85. pi, 85. rho, 85. sigma, 85. Cluster: 4608, 85.

CASSIOPEIA, Map No. 25, 133. Stars: eta, 132. iota, 132. sigma, 132. psi, 132. Temporary star: 1572 (Tycho's), 134. Cluster: 392, 134.

CEPHEUS, Map No. 25, 133.

CETUS, Map No. 20, 112. Stars: alpha, 118. gamma, 113. zeta, 111. eta, 111. 26, 111. 42, 111. Variables: omicron (Mira), 111. R, 113. S, 113.

COLUMBA, Map No. 2, 31.

COMA BERENICES, Map No. 6, 53. Stars: 2, 54. 12, 54. 17, 54. 24, 54. 35, 54. 42, 54. Clusters: 2752, 56. 3453, 56.

CORONA BOREALIS, Map No. 11, 67. Stars: gamma, 72. zeta, 73. eta, 72. nu, 73. sigma, 73. Sigma 1932, 72. Temporary star: 1866, 73.

CORVUS, Map No. 8, 58. Star: delta, 57.

CRATER, Map No. 8, 58. Variable: R, 57.

CYGNUS, Map No. 17, 99. Stars: beta (Albireo), 103. delta, 104. lambda, 105. , 105. omicron^2, 104. chi (17), 104. psi, 104. 49, 104. 52, 104. 61, 105. Temporary star: 1876, 105. Cluster: 4681, 105. Variable: chi, 104.

DELPHINUS, Map No. 16, 95. Stars: alpha, 96. beta, 96. gamma, 94.

DRACO, Map No. 15, 91; Map No. 26, 137. Stars: gamma, 93. epsilon, 93. eta, 93. , 93. nu, 93. Sigma 1984, 93. Sigma 2054, 93. Sigma 2078 (17), 93. Sigma 2323, 93. Nebulae: 4373, 93. 4415, 94.

EQUULEUS, Map No. 18, 107. Stars: beta, 109. gamma, 109. Sigma 2735, 108. Sigma 2737, 108. Sigma 2742, 108. Sigma 2744, 108.

ERIDANUS, Map No. 21, 115. Stars: gamma, 114. omicron^2, 116. 12, 114. Sigma 470 (32), 114. Sigma 516 (39), 114. Sigma 590, 116. Nebula: 826, 116.

GEMINI, Map No. 4, 39. Stars: alpha (Castor), 38. beta (Pollux), 40. gamma, 43. delta, 41. epsilon, 43. zeta, 41. eta, 42. kappa, 40. lambda, 43. , 43. pi, 40. 15, 43. 38, 43. Cluster: 1360, 42. Variables: zeta, 41. eta, 42. R, 41. S, 41. T, 41. U, 41. Nebula: 1532, 41.

HERCULES, Map No. 14, 87; Map No. 15, 91. Stars: alpha, 89. gamma, 89. delta, 89. zeta, 89. kappa, 89. , 90. rho, 90. 42, 90. 95, 90. Sigma 2101, 90. Sigma 2104, 90. Sigma 2215, 90. Sigma 2289, 90. Nebulae: 4230 (M 13), 92. 4234, 92.

HYDRA, Map No. 3, 34; Map No. 8, 58; Map No. 10, 65. Stars: alpha, 56. epsilon, 36. theta, 36. Bu. 339, 56. Sigma 1245, 36. Variable: R, 59. Nebulae: 2102, 56. 3128, 59.

LACERTA, Map No. 17, 99.

LEO, Map No. 6, 53. Stars: gamma, 52. iota, 52. tau, 52. 49, 52. 54, 52. 88, 52. 90, 52. Variable: R, 52. Nebula: 1861, 52.

LEO MINOR, Map No. 26, 137.

LEPUS, Map No. 1, 21; Map No. 2, 31. Stars: alpha, 30. beta, 30. gamma, 30. iota, 30. 45, 30. Variable: R, 29.

LIBRA, Map No. 10, 65. Stars: A, 64. alpha, 64. beta, 64. iota, 64. Variable: delta, 64.

LYNX, Map No. 5, 45. Stars: 4, 51. 5, 51. 12, 51. 14, 51. 19, 51. 38, 52. Sigma 958, 51. Sigma 1009, 51. Sigma 1333, 51.

LYRA, Map No. 17, 99. Stars: alpha (Vega), 97. beta, 100. epsilon, 98. zeta, 100. 17, 103. Variable: beta, 100. Nebula: 4447 (Ring), 102.

MONOCEROS, Map No. 1, 21; Map No. 3, 34. Stars: 4, 35. 8, 35. 11, 35. Sigma 921, 35. Sigma 938, 35. Sigma 950, 35. Sigma 1183, 35. Sigma 1190, 35. Clusters: 1424, 35. 1465, 36. 1483, 36. 1611, 36. 1637, 36. Variable: S, 35.

OPHIUCHUS, Map No. 12, 77; Map No. 14, 87. Stars: lambda, 86. tau, 86. 36, 79. 39, 79. 67, 86. 70, 86. 73, 86. Sigma 2166, 86. Sigma 2173, 86. Temporary star: 1604, 80. Clusters: 4211, 79. 4256, 88. 4264, 79. 4268, 79. 4269, 79. 4270, 79. 4315, 88. 4346, 79. 4410, 88. Variable: R, 80.

ORION, Map No. 1, 21. Stars: alpha (Betelgeuse), 27. beta (Rigel), 20. delta, 23. zeta, 23. eta, 24. theta (Trapezium), 25. iota, 27. lambda, 28. rho, 28. sigma, 24. tau, 28. psi^2, 29. Sigma 627, 28. Sigma 629, 28. Sigma 652, 28. Sigma 725, 24. Sigma 728 (A 32), 28. Sigma 729, 29. Sigma 747, 27. Sigma 750, 27. Sigma 795 (52), 27. Sigma 816, 29. Omicron Sigma 98 (i), 28. Clusters: 905, 29. 1184, 27. 1361, 29. 1376, 29. Nebulae: Great Orion Nebula, 25. 1227, 23. 1267, 29.

PEGASUS, Map No. 19, 110. Stars: beta, 109. gamma, 109. epsilon, 109. eta, 109.

PERSEUS, Map No. 24, 125. Stars: epsilon, 129. zeta, 130. eta, 129. Clusters: 512, 129. 521, 129. Variable: beta (Algol), 130.

PISCES, Map No. 18, 107; Map No. 20, 112; Map No. 22, 119. Stars: alpha, 117. zeta, 117. psi, 117. 55, 117. 65, 117. 66, 117. 77, 117. Variable: R, 118.

SAGITTA, Map No. 16, 95. Stars: epsilon, 94. zeta, 94. theta, 94. Nebula: 4572, 94.

SAGITTARIUS, Map No. 12, 77; Map No. 13, 83. Stars: , 80. 54, 84. Clusters: M 25, 81. 4355, 81. 4361 (M 8), 81. 4397 (M 24), 81. 4424, 84. Variables: R, 84. T, 84. U, 82. V, 82.

SCORPIO, Map No. 12, 77. Stars: alpha (Antares), 75. beta, 76. nu, 76. xi, 76. sigma, 76. Temporary star: 1860, 78. Clusters: 4173, 78. 4183, 78.

SCUTUM SOBIESKII, Map No. 12, 77; Map No. 13, 83. Stars: Sigma 2306, 82. Sigma 2325, 82. Clusters: 4400, 82. 4426, 82. 4437, 82. Variable: R, 82. Nebula: 4441, 82.

SERPENS, Map No. 12, 77; Map No. 14, 87. Stars: alpha, 86. beta, 86. delta, 86. theta, 88. nu, 86. Variable: R, 86.

TAURUS, Map No. 23, 121. Stars: alpha (Aldebaran), 123. eta (Alcyone), 120. theta, 123. kappa, 123. sigma, 124. tau, 124. phi, 123. chi, 123. 30, 122. Sigma 412 (7), 120. Sigma 430, 122. Sigma 674, 124. Sigma 716, 124. Clusters: Hyades, 120. Pleiades, 120. 1030, 124. Variable: lambda, 122. Nebulae: in Pleiades, 120. 1157 (Crab Net), 124.

TRIANGULUM, Map No. 24, 125. Star: 6, 129. Nebula: 352, 129.

URSA MAJOR, Map No. 26, 137. Stars: zeta (Mizar), 135. iota, 135. nu, 135. xi, 135. sigma^2, 135. 23, 135. 57, 135. 65, 135. Nebulae: 1949, 136. 1950, 136. 2343, 136.

URSA MINOR, Map No. 26, 137. Stars: alpha (Pole Star), 138. pi, 138.

VIRGO, Map No. 9, 61. Stars: alpha (Spica), 59. gamma, 59. theta, 60. 84, 62. Sigma 1669, 59. Sigma 1846, 62. Variables: R, 63. S, 63. U, 63. Nebulae: Field of the, 62. 2806, 63. 2961, 63. 3105, 63.

VULPECULA, Map No. 17, 99. Star: Sigma 2695, 106. Temporary star: 1670, 106. Nebula: 4532 (Dumb Bell), 106.

THE MOON, most interesting of telescopic objects, 156; telescopic views of moon reversed, 157. Craters, ring mountains, and ringed plains: Agatharchides, 179. Agrippa, 168. Albategnius, 171. Alhazen, 160. Aliacensis, 171. Alphonsus, 176. Archimedes, 175. Ariadaeus, 168. Aristarchus,174. Aristillus, 167. Aristoteles, 162. Arzachel, 176. Atlas, 160. Autolycus, 167. Bailly, 178. Ball, 176. Barrow, 162. Beer, 175. Berzelius, 160. Billy, 179. Bullialdus, 180. Burckhardt, 157. Capuanus, 179. Cassini, 167. Catharina, 170, Cichus, 179. Clavius, 178. Cleomenes, 159. Condorcet, 160. Copernicus, 175. Cyrillus, 170. Delisle, 174 Endymion, 160. Eratosthenes, 175. Eudoxus, 162. Euler, 174. Firmicus, 160. Fracastorius, 169, 179. Furnerius, 161. Gassendi, 179. Gauss, 159. Geminus, 160. Goclenius, 169. Godin, 168. Grimaldi, 179. Guttemberg, 169. Hainzel, 179. Hansen, 160. Helicon, 174. Hell, 176. Hercules, 160. Herodotus, 174. Herschel, Caroline, 174. Hipparchus, 171. Humboldt, 161. Hyginus, 168. Julius Caesar, 168. Kepler, 176. Lambert, 174. Landsberg, 180. Langrenus, 160, 168. Letronne, 179. Leverrier, 174. Lexell, 176. Lichtenberg, 174. Linne, 165. Longomontanus, 178. Macrobius, 159. Maginus, 178. Manilius, 166. Maurolycus, 172. Menelaus, 166. Mercator, 179. Mersenius, 179. Messala, 160. Messier, 169. Newton, 178. Petavius, 160, 168. Picard, 157. Piccolomini, 171. Pico, 172. Plato, 172. Plinius, 166. Posidonius, 163, 164. Proclus, 158. Ptolemaeus, 176. Purbach, 176. Sacrobosco, 171. Schickard, 178. Schiller, 178. Silberschlag, 168. Stoefler, 171. Sulpicius Gallus, 166. Theaetetus, 167. Thebit, 176. Theophilus, 170. Timocharis, 174. Tobias Mayer, 176. Tralles, 159. Triesnecker, 168. Tycho, 177, 178. Vendelinus, 160, 168. Vieta, 179. Vitello, 179. Walter, 171. Wargentin, 179. Werner, 171. Wilhelm I, 178. Maria, or "Seas": Lacus Somniorum, 163. Mare Crisium, 157, 159, 160. Mare Fecunditatis, 160, 168. Mare Frigoris, 162, 172. Mare Humboldtianum, 160. Mare Humorum, 176, 179. Mare Imbrium, 163, 172, 174. Mare Nectaris, 168. Mare Nubium, 176. Mare Serenitatis, 163, 164, 165. Mare Tranquilitatis, 168. Mare Vaporum, 166, 167. Oceanus Procellarum, 172, 176, 179. Palus Nebularum, 167. Palus Putredinis, 167. Palus Somnii, 159. Sinus AEstuum, 172. Sinus Iridum, 172, 173. Other formations: Alps Mountains, 163. Apennine Mountains, 163, 167, 175. Cape Agarum, 158. Cape Heraclides, 173. Cape Laplace, 173. Carpathian Mountains, 176. Caucasus Mountains, 163. Cordilleras Mountains, 180. D'Alembert Mountains, 180. Doerfel Mountains, 180. Haemus Mountains, 165. Harbinger Mountains, 174. Leibnitz Mountains, 180. "Lunar Railroad," 176. Mt. Argaeus, 165, 167. Mt. Hadley, 167. Mt. Huygens, 175. Pyrenees Mountains, 169. Taurus Mountains, 164.

THE PLANETS: Are there planets among the stars? 183. Mars, two views of, 17. best advertised of planets, 151. favorable oppositions of, 152. seen with 5-inch telescope, 152. polar caps of, 152. color of, 152. dark markings on, 152. "canals," 153. earthlike condition of, 153. Mercury, phases of, 155. peculiar rotation of, 155. markings on, 155. probably not habitable, 155. Jupiter, easiest planet for amateurs, 141. seen with 5-inch glass, 141. satellites, swift motions of, 142. velocity of planet's equator, 142. how to see all sides of, 142, 143. watching rotation of, 143. eclipses and transits of satellites, 144, 147. belts and clouds of, 145. different rates of rotation, 145. names and numbers of satellites, 146. Saturn, next to Jupiter in attractiveness, 147. seen with 5-inch glass, 148. its moons and their orbits, 148, 149. polar view of system, 149. Roche's limit, 149, 150. origin of the rings, 150. Pickering's ninth satellite, 151. the satellites as telescopic objects, 151. Venus, her wonderful brilliance, 153. her atmosphere seen, 153. Lowell's observations, 153. Schiaparelli's observations, 154. her peculiar rotation, 154. how to see, in daytime, 155. Neptune and Uranus, 155.

THE SUN, 181. shade glasses for telescopes in viewing, 181. solar prism, 181. helioscope, 181. periodicity of spots, 181. to see, by projection, 182. spectroscope for solar observation, 182.

THE TELESCOPE: refractors and reflectors, 2, 8. eyepieces, 6, 9, 10. aberration (chromatic), 6; (spherical), 6, 17. achromatic telescopes, how made, 7. object glass, 8. magnifying power, 11. mountings, 12. rules for testing, 13. image of star in, 14. image in and out of focus, 14, 15, 17. astigmatism, 16.

THE END



1692 S. Pleasures of the Telescope GARRETT P. SERVISS

This book says to the amateur, in effect:—"What if you have not all advantages of clockwork and observatory equipment. You may know something of the witchery of the heavens even with a little telescope of three to five inches aperture!" "Pleasures of the Telescope" is popular in style rather than technical. For setting forth "the chief attractions of the starry heavens," a complete set of star-maps is included, showing "all the stars visible to the naked eye in the regions of sky represented, and in addition some stars that can only be seen with optical aid." In six chapters these twenty-six maps are described so plainly that the amateur can readily find all the interesting star-groups, clusters, and nebulae, and also the colored or double stars. In the three concluding chapters the moon and planets receive special consideration. In the opening chapter the amateur is told how to select and test a glass.

Booklovers Bulletin.



Transcriber's Note

Minor errors and inconsistencies in punctuation and hyphenation have been silently corrected.

Some illustrations have been relocated a short distance within the text.

Original page numbers have been retained in the index.

Greek letters, used to identify stars, are replaced with the full name of the Greek letter, e.g. alpha. Upper case Greek letters are shown by capitalising the initial letter, e.g. Sigma 1126

A caret (^) is used to represent superscripts, e.g. nu^1 and nu^2

The following minor corrections have also been made:

p3: "wil" has been corrected to "will".

p28: Sigma 629 is not shown on Map No. 1. The location of m Orionis is marked as Sigma 696. This inconsistency has not been corrected.

p54: "for colors" has been corrected to "four colors".

p68: "1,065,790,250,000,000" has been corrected to "1,065,702,500,000,000".

p163-164: "magnical" has been corrected to "magical".

p179: A repeated "and" has been removed.

THE END