PART I.

THE ASTEROIDS, OR MINOR PLANETS BETWEEN MARS AND JUPITER.

1. Introductory. PLANETARY DISCOVERIES BEFORE THE ASTEROIDS WERE KNOWN.

The first observer who watched the skies with any degree of care could not fail to notice that while the greater number of stars maintained the same relative places, a few from night to night were ever changing their positions. The planetary character of Mercury, Venus, Mars, Jupiter, and Saturn was thus known before the dawn of history. The names, however, of those who first distinguished them as "wanderers" are hopelessly lost. Venus, the morning and evening star, was long regarded as two distinct bodies. The discovery that the change of aspect was due to a single planet's change of position is ascribed to Pythagoras.

At the beginning of the seventeenth century but six primary planets and one satellite were known as members of the solar system. Very few, even of the learned, had then accepted the theory of Copernicus; in fact, before the invention of the telescope the evidence in its favor was not absolutely conclusive. On the 7th of January, 1610, Galileo first saw the satellites of Jupiter. The bearing of this discovery on the theory of the universe was sufficiently obvious. Such was the prejudice, however, against the Copernican system that some of its opponents denied even the reality of Galileo's discovery. "Those satellites," said a Tuscan astronomer, "are invisible to the naked eye, and therefore can exercise no influence on the earth, and therefore would be useless, and therefore do not exist. Besides, the Jews and other ancient nations, as well as modern Europeans, have adopted the division of the week into seven days, and have named them from the seven planets; now, if we increase the number of planets this whole system falls to the ground."

No other secondary planet was discovered till March 25, 1655, when Titan, the largest satellite of Saturn, was detected by Huyghens. About two years later (December 7, 1657) the same astronomer discovered the true form of Saturn's ring; and before the close of the century (1671-1684) four more satellites, Japetus, Rhea, Tethys, and Dione, were added to the Saturnian system by the elder Cassini. Our planetary system, therefore, as known at the close of the seventeenth century, consisted of six primary and ten secondary planets.

Nearly a century had elapsed from the date of Cassini's discovery of Dione, when, on the 13th of March, 1781, Sir William Herschel enlarged the dimensions of our system by the detection of a planet—Uranus—exterior to Saturn. A few years later (1787-1794) the same distinguished observer discovered the first and second satellites of Saturn, and also the four Uranian satellites. He was the only planet discoverer of the eighteenth century.

2. Discovery of the First Asteroids.

As long ago as the commencement of the seventeenth century the celebrated Kepler observed that the respective distances of the planets from the sun formed nearly a regular progression. The series, however, by which those distances were expressed required the interpolation of a term between Mars and Jupiter,—a fact which led the illustrious German to predict the discovery of a planet in that interval. This conjecture attracted but little attention till after the discovery of Uranus, whose distance was found to harmonize in a remarkable manner with Kepler's order of progression. Such a coincidence was of course regarded with considerable interest. Towards the close of the last century Professor Bode, who had given the subject much attention, published the law of distances which bears his name, but which, as he acknowledged, is due to Professor Titius. According to this formula the distances of the planets from Mercury's orbit form a geometrical series of which the ratio is two. In other words, if we reckon the distances of Venus, the earth, etc., from the orbit of Mercury, instead of from the sun, we find that—interpolating a term between Mars and Jupiter—the distance of any member of the system is very nearly half that of the next exterior. Baron De Zach, an enthusiastic astronomer, was greatly interested in Bode's empirical scheme, and undertook to determine the elements of the hypothetical planet. In 1800 a number of astronomers met at Lilienthal, organized an astronomical society, and assigned one twenty-fourth part of the zodiac to each of twenty-four observers, in order to detect, if possible, the unseen planet. When it is remembered that at this time no primary planet had been discovered within the ancient limits of the solar system, that the object to be looked for was comparatively near us, and that the so-called law of distances was purely empirical, the prospect of success, it is evident, was extremely uncertain. How long the watch, if unsuccessful, might have been continued is doubtful. The object of research, however, was fortunately brought to light before the members of the astronomical association had fairly commenced their labors.[1]

On the 1st of January, 1801, Professor Giuseppe Piazzi, of Palermo, noticed a star of the eighth magnitude, not indicated in Wollaston's catalogue. Subsequent observations soon revealed its planetary character, its mean distance corresponding very nearly with the calculations of De Zach. The discoverer called it Ceres Ferdinandea, in honor of his sovereign, the King of Naples. In this, however, he was not followed by astronomers, and the planet is now known by the name of Ceres alone. The discovery of this body was hailed by astronomers with the liveliest gratification as completing the harmony of the system. What, then, was their surprise when in the course of a few months this remarkable order was again interrupted! On the 28th of March, 1802, Dr. William Olbers, of Bremen, while examining the relative positions of the small stars along the path of Ceres, in order to find that planet with the greater facility, noticed a star of the seventh or eighth magnitude, forming with two others an equilateral triangle where he was certain no such configuration existed a few months before. In the course of a few hours its motion was perceptible, and on the following night it had very sensibly changed its position with respect to the neighboring stars. Another planet was therefore detected, and Dr. Olbers immediately communicated his discovery to Professor Bode and Baron De Zach. In his letter to the former he suggested Pallas as the name of the new member of the system,—a name which was at once adopted. Its orbit, which was soon computed by Gauss, was found to present several striking anomalies. The inclination of its plane to that of the ecliptic was nearly thirty-five degrees,—an amount of deviation altogether extraordinary. The eccentricity also was greater than in the case of any of the old planets. These peculiarities, together with the fact that the mean distances of Ceres and Pallas were nearly the same, and that their orbits approached very near each other at the intersection of their planes, suggested the hypothesis that they are fragments of a single original planet, which, at a very remote epoch, was disrupted by some mysterious convulsion. This theory will be considered when we come to discuss the tabulated elements of the minor planets now known.

For the convenience of astronomers, Professor Harding, of Lilienthal, undertook the construction of charts of all the small stars near the orbits of Ceres and Pallas. On the evening of September 1, 1804, while engaged in observations for this purpose, he noticed a star of the eighth magnitude not mentioned in the great catalogue of Lalande. This proved to be a third member of the group of asteroids. The discovery was first announced to Dr. Olbers, who observed the planet at Bremen on the evening of September 7.

Before Ceres had been generally adopted by astronomers as the name of the first asteroid, Laplace had expressed a preference for Juno. This, however, the discoverer was unwilling to accept. Mr. Harding, like Laplace, deeming it appropriate to place Juno near Jupiter, selected the name for the third minor planet, which is accordingly known by this designation.

Juno is distinguished among the first asteroids by the great eccentricity of its orbit, amounting to more than 0.25. Its least and its greatest distances from the sun are therefore to each other very nearly in the ratio of three to five. The planet consequently receives nearly three times as much light and heat in perihelion as in aphelion. It follows, also, that the half of the orbit nearest the sun is described in about eighteen months, while the remainder, or more distant half, is not passed over in much less than three years. Schroeter noticed a variation in the light of Juno, which he supposed to be produced by an axial rotation in about twenty-seven hours.

The fact that Juno was discovered not far from the point at which the orbit of Pallas approaches very near that of Ceres, was considered a strong confirmation of the hypothesis that the asteroids were produced by the explosion of a large planet; for in case this hypothesis be founded in truth, it is evident that whatever may have been the forms of the various orbits assumed by the fragments, they must all return to the point of separation. In order, therefore, to detect other members of the group, Dr. Olbers undertook a systematic examination of the two opposite regions of the heavens through which they must pass. This search was prosecuted with great industry and perseverance till ultimately crowned with success. On the 29th of March, 1807, while sweeping over one of those regions through which the orbits of the known asteroids passed, a star of the sixth magnitude was observed where none had been seen at previous examinations. Its planetary character, which was immediately suspected, was confirmed by observation, its motion being detected on the very evening of its discovery. This fortunate result afforded the first instance of the discovery of two primary planets by the same observer.

The astronomer Gauss having been requested to name the new planet, fixed upon Vesta, a name universally accepted. Though the brightest of the asteroids, its apparent diameter is too small to be accurately determined, and hence its real magnitude is not well ascertained. Professor Harrington, of Ann Arbor, has estimated the diameter at five hundred and twenty miles. According to others, however, it does not exceed three hundred. If the latter be correct, the volume is about 1/20000 that of the earth. It is remarkable that notwithstanding its diminutive size it may be seen under favorable circumstances by the naked eye.

Encouraged by the discovery of Vesta (which he regarded as almost a demonstration of his favorite theory), Dr. Olbers continued his systematic search for other planetary fragments. Not meeting, however, with further success, he relinquished his observations in 1816. His failure, it may here be remarked, was doubtless owing to the fact that his examination was limited to stars of the seventh and eighth magnitudes.

The search for new planets was next resumed about 1831, by Herr Hencke, of Driessen. With a zeal and perseverance worthy of all praise, this amateur astronomer employed himself in a strict examination of the heavens represented by the Maps of the Berlin Academy. These maps extend fifteen degrees on each side of the equator, and contain all stars down to the ninth magnitude and many of the tenth. Dr. Hencke rendered some of these charts still more complete by the insertion of smaller stars; or rather, "made for himself special charts of particular districts." On the evening of December 8, 1845, he observed a star of the ninth magnitude where none had been previously seen, as he knew from the fact that it was neither found on his own chart nor given on that of the Academy. On the next morning he wrote to Professors Encke and Schumacher informing them of his supposed discovery. "It is very improbable," he remarked in his letter to the latter, "that this should prove to be merely a variable star, since in my former observations of this region, which have been continued for many years, I have never detected the slightest trace of it." The new star was soon seen at the principal observatories of Europe, and its planetary character satisfactorily established. The selection of a name was left by the discoverer to Professor Encke, who chose that of Astræa.

The facts in regard to the very numerous subsequent discoveries may best be presented in a tabular form.

TABLE I. The Asteroids in the Order of their Discovery.

Asteroids.Date of Discovery.Name of Discoverer.Place of Discovery.

1. Ceres1801, Jan. 1PiazziPalermo

2. Pallas1802, Mar. 28OlbersBremen

3. Juno1804, Sept. 1HardingLilienthal

4. Vesta1807, Mar. 29OlbersBremen

5. Astræa1845, Dec. 8HenckeDriessen

6. Hebe1847, July 1HenckeDriessen

7. Iris1847, Aug. 14HindLondon

8. Flora1847, Oct. 18HindLondon

9. Metis1848, Apr. 26GrahamMarkree

10. Hygeia1849, Apr. 12De GasparisNaples

11. Parthenope1850, May 11De GasparisNaples

12. Victoria1850, Sept. 13HindLondon

13. Egeria1850, Nov. 2De GasparisNaples

14. Irene1851, May 19HindLondon

15. Eunomia1851, July 29De GasparisNaples

16. Psyche1852, Mar. 17De GasparisNaples

17. Thetis1852, Apr. 17LutherBilk

18. Melpomene1852, June 24HindLondon

19. Fortuna1852, Aug. 22HindLondon

20. Massalia1852, Sept. 19De GasparisNaples

21. Lutetia1852, Nov. 15GoldschmidtParis

22. Calliope1852, Nov. 16HindLondon

23. Thalia1852, Dec. 15HindLondon

24. Themis1853, Apr. 5De GasparisNaples

25. Phocea1853, Apr. 6ChacornacMarseilles

26. Proserpine1853, May 5LutherBilk

27. Euterpe1853, Nov. 8HindLondon

28. Bellona1854, Mar. 1LutherBilk

29. Amphitrite1854, Mar. 1MarthLondon

30. Urania1854, July 22HindLondon

31. Euphrosyne1854, Sept. 1FergusonWashington

32. Pomona1854, Oct. 26GoldschmidtParis

33. Polyhymnia1854, Oct. 28ChacornacParis

34. Circe1855, Apr. 6ChacornacParis

35. Leucothea1855, Apr. 19LutherBilk

36. Atalanta1855, Oct. 5GoldschmidtParis

37. Fides1855, Oct. 5LutherBilk

38. Leda1856, Jan. 12ChacornacParis

39. Lætitia1856, Feb. 8ChacornacParis

40. Harmonia1856, Mar. 31GoldschmidtParis

41. Daphne1856, May 22GoldschmidtParis

42. Isis1856, May 23PogsonOxford

43. Ariadne1857, Apr. 15PogsonOxford

44. Nysa1857, May 27GoldschmidtParis

45. Eugenia1857, June 27GoldschmidtParis

46. Hestia1857, Aug. 16PogsonOxford

47. Aglaia1857, Sept. 15LutherBilk

48. Doris1857, Sept. 19GoldschmidtParis

49. Pales1857, Sept. 19GoldschmidtParis

50. Virginia1857, Oct. 4FergusonWashington

51. Nemausa1858, Jan. 22LaurentNismes

52. Europa1858, Feb. 4GoldschmidtParis

53. Calypso1858, Apr. 4LutherBilk

54. Alexandra1858, Sept. 10GoldschmidtParis

55. Pandora1858, Sept. 10SearleAlbany

56. Melete1857, Sept. 9GoldschmidtParis

57. Mnemosyne1859, Sept. 22LutherBilk

58. Concordia1860, Mar. 24LutherBilk

59. Olympia1860, Sept. 12ChacornacParis

60. Echo1860, Sept. 16FergusonWashington

61. Danaë1860, Sept. 9GoldschmidtParis

62. Erato1860, Sept. 14Foerster and LesserBerlin

63. Ausonia1861, Feb. 10De GasparisNaples

64. Angelina1861, Mar. 4TempelMarseilles

65. Maximiliana1861, Mar. 8TempelMarseilles

66. Maia1861, Apr. 9TuttleCambridge, U.S.

67. Asia1861, Apr. 17PogsonMadras

68. Leto1861, Apr. 29LutherBilk

69. Hesperia1861, Apr. 29SchiaparelliMilan

70. Panopea1861, May 5GoldschmidtParis

71. Niobe1861, Aug. 13LutherBilk

72. Feronia1862, May 29Peters and SaffordClinton

73. Clytie1862, Apr. 7TuttleCambridge

74. Galatea1862, Aug. 29TempelMarseilles

75. Eurydice1862, Sept. 22PetersClinton

76. Freia1862, Oct. 21D'ArrestCopenhagen

77. Frigga1862, Nov. 12PetersClinton

78. Diana1863, Mar. 15LutherBilk

79. Eurynome1863, Sept. 14WatsonAnn Arbor

80. Sappho1864, May 2PogsonMadras

81. Terpsichore1864, Sept. 30TempelMarseilles

82. Alcmene1864, Nov. 27LutherBilk

83. Beatrix1865, Apr. 26De GasparisNaples

84. Clio1865, Aug. 25LutherBilk

85. Io1865, Sept. 19PetersClinton

86. Semele1866, Jan. 14TietjenBerlin

87. Sylvia1866, May 16PogsonMadras

88. Thisbe1866, June 15PetersClinton

89. Julia1866, Aug. 6StephanMarseilles

90. Antiope1866, Oct. 1LutherBilk

91. Ægina1866, Nov. 4BorellyMarseilles

92. Undina1867, July 7PetersClinton

93. Minerva1867, Aug. 24WatsonAnn Arbor

94. Aurora1867, Sept. 6WatsonAnn Arbor

95. Arethusa1867, Nov. 24LutherBilk

96. Ægle1868, Feb. 17CoggiaMarseilles

97. Clotho1868, Feb. 17CoggiaMarseilles

98. Ianthe1868, Apr. 18PetersClinton

99. Dike1868, May 28BorellyMarseilles

100. Hecate1868, July 11WatsonAnn Arbor

101. Helena1868, Aug. 15WatsonAnn Arbor

102. Miriam1868, Aug. 22PetersClinton

103. Hera1868, Sept. 7WatsonAnn Arbor

104. Clymene1868, Sept. 13WatsonAnn Arbor

105. Artemis1868, Sept. 16WatsonAnn Arbor

106. Dione1868, Oct. 10WatsonAnn Arbor

107. Camilla1868, Nov. 17PogsonMadras

108. Hecuba1869, Apr. 2LutherBilk

109. Felicitas1869, Oct. 9PetersClinton

110. Lydia1870, Apr. 19BorellyMarseilles

111. Ate1870, Aug. 14PetersClinton

112. Iphigenia1870, Sept. 19PetersClinton

113. Amalthea1871, Mar. 12LutherBilk

114. Cassandra1871, July 23PetersClinton

115. Thyra1871, Aug. 6WatsonAnn Arbor

116. Sirona1871, Sept. 8PetersClinton

117. Lomia1871, Sept. 12BorellyMarseilles

118. Peitho1872, Mar. 15LutherBilk

119. Althea1872, Apr. 3WatsonAnn Arbor

120. Lachesis1872, Apr. 10BorellyMarseilles

121. Hermione1872, May 12WatsonAnn Arbor

122. Gerda1872, July 31PetersClinton

123. Brunhilda1872, July 31PetersClinton

124. Alceste1872, Aug. 23PetersClinton

125. Liberatrix1872, Sept. 11Prosper HenryParis

126. Velleda1872, Nov. 5Paul HenryParis

127. Johanna1872, Nov. 5Prosper HenryParis

128. Nemesis1872, Nov. 25WatsonAnn Arbor

129. Antigone1873, Feb. 5PetersClinton

130. Electra1873, Feb. 17PetersClinton

131. Vala1873, May 24PetersClinton

132. Æthra1873, June 13WatsonAnn Arbor

133. Cyrene1873, Aug. 16WatsonAnn Arbor

134. Sophrosyne1873, Sept. 27LutherBilk

135. Hertha1874, Feb. 18PetersClinton

136. Austria1874, Mar. 18PalisaPola

137. Melibœa1874, Apr. 21PalisaPola

138. Tolosa1874, May 19PerrotinToulouse

139. Juewa1874, Oct. 10WatsonPekin

140. Siwa1874, Oct. 13PalisaPola

141. Lumen1875, Jan. 13Paul HenryParis

142. Polana1875, Jan. 28PalisaPola

143. Adria1875, Feb. 23PalisaPola

144. Vibilia1875, June 3PetersClinton

145. Adeona1875, June 3PetersClinton

146. Lucina1875, June 8BorellyMarseilles

147. Protogenea1875, July 10SchulhofVienna

148. Gallia1875, Aug. 7Prosper HenryParis

149. Medusa1875, Sept. 21PerrotinToulouse

150. Nuwa1875, Oct. 18WatsonAnn Arbor

151. Abundantia1875, Nov. 1PalisaPola

152. Atala1875, Nov. 2Paul HenryParis

153. Hilda1875, Nov. 2PalisaPola

154. Bertha1875, Nov. 4Prosper HenryParis

155. Scylla1875, Nov. 8PalisaPola

156. Xantippe1875, Nov. 22PalisaPola

157. Dejanira1875, Dec. 1BorellyMarseilles

158. Coronis1876, Jan. 4KnorreBerlin

159. Æmilia1876, Jan. 26Paul HenryParis

160. Una1876, Feb. 20PetersClinton

161. Athor1876, Apr. 19WatsonAnn Arbor

162. Laurentia1876, Apr. 21Prosper HenryParis

163. Erigone1876, Apr. 26PerrotinToulouse

164. Eva1876, July 12Paul HenryParis

165. Loreley1876, Aug. 9PetersClinton

166. Rhodope1876, Aug. 15PetersClinton

167. Urda1876, Aug. 28PetersClinton

168. Sibylla1876, Sept. 27WatsonAnn Arbor

169. Zelia1876, Sept. 28Prosper HenryParis

170. Maria1877, Jan. 10PerrotinToulouse

171. Ophelia1877, Jan. 13BorellyMarseilles

172. Baucis1877, Feb. 5BorellyMarseilles

173. Ino1877, Aug. 1BorellyMarseilles

174. Phædra1877, Sept. 2WatsonAnn Arbor

175. Andromache1877, Oct. 1WatsonAnn Arbor

176. Idunna1877, Oct. 14PetersClinton

177. Irma1877, Nov. 5Paul HenryParis

178. Belisana1877, Nov. 6PalisaPola

179. Clytemnestra1877, Nov. 11WatsonAnn Arbor

180. Garumna1878, Jan. 29PerrotinToulouse

181. Eucharis1878, Feb. 2CottenotMarseilles

182. Elsa1878, Feb. 7PalisaPola

183. Istria1878, Feb. 8PalisaPola

184. Deiopea1878, Feb. 28PalisaPola

185. Eunice1878, Mar. 1PetersClinton

186. Celuta1878, Apr. 6Prosper HenryParis

187. Lamberta1878, Apr. 11CoggiaMarseilles

188. Menippe1878, June 18PetersClinton

189. Phthia1878, Sept. 9PetersClinton

190. Ismene1878, Sept. 22PetersClinton

191. Kolga1878, Sept. 30PetersClinton

192. Nausicaa1879, Feb. 17PalisaPola

193. Ambrosia1879, Feb. 28CoggiaMarseilles

194. Procne1879, Mar. 21PetersClinton

195. Euryclea1879, Apr. 22PalisaPola

196. Philomela1879, May 14PetersClinton

197. Arete1879, May 21PalisaPola

198. Ampella1879, June 13BorellyMarseilles

199. Byblis1879, July 9PetersClinton

200. Dynamene1879, July 27PetersClinton

201. Penelope1879, Aug. 7PalisaPola

202. Chryseis1879, Sept. 11PetersClinton

203. Pompeia1879, Sept. 25PetersClinton

204. Callisto1879, Oct. 8PalisaPola

205. Martha1879, Oct. 13PalisaPola

206. Hersilia1879, Oct. 13PetersClinton

207. Hedda1879, Oct. 17PalisaPola

208. Lachrymosa1879, Oct. 21PalisaPola

209. Dido1879, Oct. 22PetersClinton

210. Isabella1879, Nov. 12PalisaPola

211. Isolda1879, Dec. 10PalisaPola

212. Medea1880, Feb. 6PalisaPola

213. Lilæa1880, Feb. 16PetersClinton

214. Aschera1880, Feb. 26PalisaPola

215. Œnone1880, Apr. 7KnorreBerlin

216. Cleopatra1880, Apr. 10PalisaPola

217. Eudora1880, Aug. 30CoggiaMarseilles

218. Bianca1880, Sept. 4PalisaPola

219. Thusnelda1880, Sept. 20PalisaPola

220. Stephania1881, May 19PalisaVienna

221. Eos1882, Jan. 18PalisaVienna

222. Lucia1882, Feb. 9PalisaVienna

223. Rosa1882, Mar. 9PalisaVienna

224. Oceana1882, Mar. 30PalisaVienna

225. Henrietta1882, Apr. 19PalisaVienna

226. Weringia1882, July 19PalisaVienna

227. Philosophia1882, Aug. 12Paul HenryParis

228. Agathe1882, Aug. 19PalisaVienna

229. Adelinda1882, Aug. 22PalisaVienna

230. Athamantis1882, Sept. 3De BallBothcamp

231. Vindobona1882, Sept. 10PalisaVienna

232. Russia1883, Jan. 31PalisaVienna

233. Asterope1883, May 11BorellyMarseilles

234. Barbara1883, Aug. 13PetersClinton

235. Caroline1883, Nov. 29PalisaVienna

236. Honoria1884, Apr. 26PalisaVienna

237. Cœlestina1884, June 27PalisaVienna

238. Hypatia1884, July 1KnorreBerlin

239. Adrastea1884, Aug. 18PalisaVienna

240. Vanadis1884, Aug. 27BorellyMarseilles

241. Germania1884, Sept. 12LutherDusseldorf

242. Kriemhild1884, Sept. 22PalisaVienna

243. Ida1884, Sept. 29PalisaVienna

244. Sita1884, Oct. 14PalisaVienna

245. Vera1885, Feb. 6PogsonMadras

246. Asporina1885, Mar. 6BorellyMarseilles

247. Eukrate1885, Mar. 14LutherDusseldorf

248. Lameia1885, June 5PalisaVienna

249. Ilse1885, Aug. 17PetersClinton

250. Bettina1885, Sept. 3PalisaVienna

251. Sophia1885, Oct. 4PalisaVienna

252. Clementina1885, Oct. 27PerrotinNice

253. Mathilde1885, Nov. 12PalisaVienna

254. Augusta1886, Mar. 31PalisaVienna

255. Oppavia1886, Mar. 31PalisaVienna

256. Walpurga1886, Apr. 3PalisaVienna

257. Silesia1886, Apr. 5PalisaVienna

258. Tyche1886, May 4LutherDusseldorf

259. Aletheia1886, June 28PetersClinton

260. Huberta1886, Oct. 3PalisaVienna

261. Prymno1886, Oct. 31PetersClinton

262. Valda1886, Nov. 3PalisaVienna

263. Dresda1886, Nov. 3PalisaVienna

264. Libussa1886, Dec. 17PetersClinton

265. Anna1887, Feb. 25PalisaVienna

266. Aline1887, May 17PalisaVienna

267. Tirza1887, May 27CharloisNice

268.1887, June 9BorellyMarseilles

269.1887, Sept. 21PalisaVienna

270.1887, Oct. 8PetersClinton

271.1887, Oct. 16KnorreBerlin

3. Remarks on Table I.

The numbers discovered by the thirty-five observers are respectively as follows:

Palisa 60

Peters 47

Luther 23

Watson 22

Borelly 15

Goldschmidt 14

Hind 10

De Gasparis 9

Pogson 8

Paul Henry 7

Prosper Henry 7

Chacornac 6

Perrotin 6

Coggia 5

Knorre 4

Tempel 4

Ferguson 3

Olbers 2

Hencke 2

Tuttle 2

Foerster (with Lesser) 1

Safford (with Peters) 1

and Messrs. Charlois, Cottenot, D'Arrest, De Ball, Graham, Harding, Laurent, Piazzi, Schiaparelli, Schulhof, Stephan, Searle, and Tietjen, each 1

Before arrangements had been made for the telegraphic transmission of discoveries between Europe and America, or even between the observatories of Europe, the same planet was sometimes independently discovered by different observers. For example, Virginia was found by Ferguson, at Washington, on October 4, 1857, and by Luther, at Bilk, fifteen days later. In all cases, however, credit has been given to the first observer.

Hersilia, the two hundred and sixth of the group, was lost before sufficient observations were obtained for determining its elements. It was not rediscovered till December 14, 1884. Menippe, the one hundred and eighty-eighth, was also lost soon after its discovery in 1878. It has not been seen for more than nine years, and considerable uncertainty attaches to its estimated elements.

Of the two hundred and seventy-one members now known (1887), one hundred and ninety-one have been discovered in Europe, seventy-four in America, and six in Asia. The years of most successful search, together with the number discovered in each, were:

Asteroids.

187920

187517

186812

187812

And six has been the average yearly number since the commencement of renewed effort in 1845. All the larger members of the group have, doubtless, been discovered. It seems not improbable, however, that an indefinite number of very small bodies belonging to the zone remain to be found. The process of discovery is becoming more difficult as the known number increases. The astronomer, for instance, who may discover number two hundred and seventy-two must know the simultaneous positions of the two hundred and seventy-one previously detected before he can decide whether he has picked up a new planet or merely rediscovered an old one. The numbers discovered in the several months are as follows:

January 13

February 23

March 19

April 35

May 21

June 13

July 14

August 28

September 46

October 28

November 26

December 5

This obvious disparity is readily explained. The weather is favorable for night watching in April and September; the winter months are too cold for continuous observations; and the small numbers in June and July may be referred to the shortness of the nights.

4. Mode of Discovery.

The astronomer who would undertake the search for new asteroids must supply himself with star-charts extending some considerable distance on each side of the ecliptic, and containing all telescopic stars down to the thirteenth or fourteenth magnitude. The detection of a star not found in the chart of a particular section will indicate its motion, and hence its planetary character. The construction of such charts has been a principal object in the labors of Dr. Peters, at Clinton, New York. In fact, his discovery of minor planets has in most instances been merely an incidental result of his larger and more important work.

NAMES AND SYMBOLS.

The fact that the names of female deities in the Greek and Roman mythologies had been given to the first asteroids suggested a similar course in the selection of names after the new epoch of discovery in 1845. While conformity to this rule has been the general aim of discoverers, the departures from it have been increasingly numerous. The twelfth asteroid, discovered in London, was named Victoria, in honor of the reigning sovereign; the twentieth and twenty-fifth, detected at Marseilles,[2] received names indicative of the place of their discovery; Lutetia, the first found at Paris, received its name for a similar purpose; the fifty-fourth was named Alexandra, for Alexander von Humboldt; the sixty-seventh, found by Pogson at Madras, was named Asia, to commemorate the fact that it was the first discovered on that continent. We find, also, Julia, Bertha, Xantippe, Zelia, Maria, Isabella, Martha, Dido, Cleopatra, Barbara, Ida, Augusta, and Anna. Why these were selected we will not stop to inquire.

As the number of asteroids increased it was found inconvenient to designate them individually by particular signs, as in the case of the old planets. In 1849, Dr. B. A. Gould proposed to represent them by the numbers expressing their order of discovery enclosed in a small circle. This method was at once very generally adopted.

5. Magnitudes of the Asteroids.

The apparent diameter of the largest is less than one-second of arc. They are all too small, therefore, to be accurately measured by astronomical instruments. From photometric observations, however, Argelander,[3] Stone,[4] and Pickering[5] have formed estimates of the diameters, the results giving probably close approximations to the true magnitudes. According to these estimates the diameter of the largest, Vesta, is about three hundred miles, that of Ceres about two hundred, and those of Pallas and Juno between one and two hundred. The diameters of about thirty are between fifty and one hundred miles, and those of all others less than fifty; the estimates for Menippe and Eva giving twelve and thirteen miles respectively. The diameter of the former is to that of the earth as one to six hundred and sixty-four; and since spheres are to each other as the cubes of their diameters, it would require two hundred and ninety millions of such asteroids to form a planet as large as our globe. In other words, if the earth be represented by a sphere one foot in diameter, the magnitude of Menippe on the same scale would be that of a sand particle whose diameter is one fifty-fifth of an inch. Its surface contains about four hundred and forty square miles,—an area equal to a county twenty-one miles square. The surface attractions of two planets having the same density are to each other as their diameters. A body, therefore, weighing two hundred pounds at the earth's surface would on the surface of the asteroid weigh less than five ounces. At the earth's surface a weight falls sixteen feet the first second, at the surface of Menippe it would fall about one-fourth of an inch. A person might leap from its surface to a height of several hundred feet, in which case he could not return in much less than an hour. "But of such speculations," Sir John Herschel remarks, "there is no end."

The number of these planetules between the orbits of Mars and Jupiter in all probability can never be known. It was estimated by Leverrier that the quantity of matter contained in the group could not be greater than one-fourth of the earth's mass. But this would be equal to five thousand planets, each as large as Vesta, to seventy-two millions as large as Menippe, or to four thousand millions of five miles in diameter. In short, the existence of an indefinite number too small for detection by the most powerful glasses is by no means improbable. The more we study this wonderful section of the solar system, the more mystery seems to envelop its origin and constitution.

6. The Orbits of the Asteroids.

The form, magnitude, and position of a planet's orbit are determined by the following elements:

1. The semi-axis major, or mean distance, denoted by the symbol a.

2. The eccentricity, e.

3. The longitude of the perihelion, π.

4. The longitude of the ascending node, ☊.

5. The inclination, or the angle contained between the plane of the orbit and that of the ecliptic, i.

And in order to compute a planet's place in its orbit for any given time we must also know

6. Its period, P, and

7. Its mean longitude, l, at a given epoch.

These elements, except the last, are given for all the asteroids, so far as known, in Table II. In column first the number denoting the order of discovery is attached to each name.

TABLE II. Elements of the Asteroids.

NameaPeπ☊i

149. Medusa2.13271137.7d0.1194 246°37´ 342°13´ 1°6´

244. Sita2.17651172.80.1370 138 20837 250

228. Agathe2.20091192.60.2405 32923 31318 233

8. Flora2.20141193.30.1567 3254 11018 553

43. Ariadne2.20331194.50.1671 27758 26435 328

254. Augusta2.20601196.80.1227 26047 289 436

72. Feronia2.26611246.00.1198 30758 20749 524

40. Harmonia2.26731247.00.0466 054 9335 416

207. Hedda2.28391260.70.0301 2172 2851 349

136. Austria2.28631262.70.0849 3166 1867 933

18. Melpomene2.29561270.40.2177 156 1504 109

80. Sappho2.29621270.90.2001 35518 21844 837

261. Prymno2.30621278.40.0794 17935 9633 338

12. Victoria2.33421302.70.2189 30139 23535 823

27. Euterpe2.34721313.50.1739 8759 9351 136

219. Thusnelda2.35421319.40.2247 34034 20044 1047

163. Erigone2.35601320.90.1567 9346 1592 442

169. Zelia2.35771322.30.1313 32620 35438 531

4. Vesta2.36161325.60.0884 25057 10329 78

186. Celuta2.36231326.20.1512 32724 1434 136

84. Clio2.36291326.70.2360 33920 32728 922

51. Nemausa2.36521328.60.0672 17443 17552 957

220. Stephania2.36661329.80.2653 33253 25824 735

30. Urania2.36671329.90.1266 3146 30812 26

105. Artemis2.37441336.40.1749 24238 1883 2131

113. Amalthea2.37611337.80.0874 19844 12311 52

115. Thyra2.37911340.30.1939 432 3095 1135

161. Athor2.37921340.50.1389 31040 1827 93

172. Baucis2.37941340.60.1139 32923 33150 102

249. Ilse2.37951340.60.2195 1417 33449 940

230. Athamantis2.38421344.60.0615 1731 23933 926

7. Iris2.38621346.40.2308 4123 25948 528

9. Metis2.38661346.70.1233 714 6832 536

234. Barbara2.38731347.30.2440 33326 1449 1522

60. Echo2.39341352.40.1838 9836 1925 335

63. Ausonia2.39791356.30.1239 27025 33758 548

25. Phocea2.40051358.50.2553 30248 20827 2135

192. Nausicaa2.40141359.30.2413 34319 16046 650

20. Massalia2.40241365.80.1429 997 20636 041

265. Anna2.40961366.20.2628 22618 33526 2524

182. Elsa2.41571371.40.1852 5152 10630 20

142. Polana2.41941374.50.1322 21954 31734 214

67. Asia2.42041375.40.1866 30635 20247 559

44. Nysa2.42231377.00.1507 11157 13111 342

6. Hebe2.42541379.30.2034 1516 13843 1047

83. Beatrix2.43011383.60.0859 19146 2732 50

135. Hertha2.43031383.80.2037 32011 3443 219

131. Vala2.43181385.10.0683 22250 6515 458

112. Iphigenia2.43351386.60.1282 3389 3243 237

21. Lutetia2.43541388.20.1621 3274 8028 35

118. Peitho2.43841390.80.1608 7736 4730 748

126. Velleda2.43991392.10.1061 34746 237 256

42. Isis2.44011392.20.2256 31758 8428 835

19. Fortuna2.44151394.40.1594 313 21127 133

79. Eurynome2.44361395.20.1945 4422 20644 437

138. Tolosa2.44921400.00.1623 31139 5452 314

189. Phthia2.45051401.10.0356 650 20322 510

11. Parthenope2.45291403.20.0994 3182 12511 437

178. Belisana2.45831407.80.1266 2780 5017 25

198. Ampella2.45951408.90.2266 35446 26845 920

248. Lameia2.47141419.10.0656 24840 24634 41

17. Thetis2.47261420.10.1293 26137 12524 536

46. Hestia2.52651466.80.1642 35414 18131 217

89. Julia2.55101488.20.1805 35313 31142 1611

232. Russia2.55221489.30.1754 20025 15230 64

29. Amphitrite2.55451491.30.0742 5623 35641 67

170. Maria2.55491491.70.0639 9547 30120 1423

262. Valda2.56351496.40.2172 6142 3840 746

258. Tyche2.56431499.80.1966 1542 2084 1450

134. Sophrosyne2.56471500.30.1165 6733 34622 1136

264. Libussa2.56721502.40.0925 07 5023 1029

193. Ambrosia2.57581510.00.2854 7052 35115 1139

13. Egeria2.57651510.60.0871 12010 4312 1632

5. Astræa2.57861512.40.1863 13457 14128 519

119. Althea2.58241515.70.0815 1129 20357 545

157. Dejanira2.58281516.10.2105 10724 6231 122

101. Helena2.58491518.00.1386 32715 34346 1011

32. Pomona2.58731520.10.0830 19322 22043 529

91. Ægina2.58951522.10.1087 8022 117 28

14. Irene2.58961522.10.1627 18019 8648 98

111. Ate2.59271524.80.1053 10842 30613 457

151. Abundantia2.59321525.30.0356 17355 3848 630

56. Melete2.60101532.20.2340 29450 1941 82

132. Æthra2.60251533.50.3799 15224 2602 250

214. Aschera2.61111541.10.0316 11555 34230 327

70. Panopea2.61391543.60.1826 29949 4818 1138

194. Procne2.61591545.40.2383 31933 15919 1824

53. Calypso2.61751546.80.2060 9252 14358 57

78. Diana2.61941548.50.2088 12142 33358 840

124. Alceste2.62971557.60.0784 24542 18826 256

23. Thalia2.63061558.40.2299 12358 6745 1014

164. Eva2.63141559.10.3471 35932 7728 2425

15. Eunomia2.64371570.00.1872 2752 18826 256

37. Fides2.64401570.30.1758 6626 821 37

66. Maia2.64541571.60.1750 488 817 36

224. Oceana2.64651572.60.0455 27051 35318 552

253. Mathilde2.64691572.90.2620 33339 1803 637

50. Virginia2.65201577.40.2852 109 17345 248

144. Vibilia2.65301578.40.2348 79 7647 448

85. Io2.65391579.20.1911 32235 20356 1153

26. Proserpine2.65611581.10.0873 23625 4555 336

233. Asterope2.65961584.30.1010 34436 22225 739

102. Miriam2.66191586.30.3035 35439 21158 54

240. Vanadis2.66381588.00.2056 5153 11454 26

73. Clytie2.66521589.30.0419 5755 751 224

218. Bianca2.66531589.30.1155 23014 17050 1513

141. Lumen2.66661590.50.2115 1343 3197 1157

77. Frigga2.66801591.80.1318 5847 20 228

3. Juno2.66831592.00.2579 5450 17053 131

97. Clotho2.67081594.30.2550 6532 16037 1146

75. Eurydice2.67201595.30.3060 33533 35956 51

145. Adeona2.67241595.40.1406 11753 7741 1238

204. Callisto2.67321596.40.1752 25745 20540 819

114. Cassandra2.67581598.80.1401 1536 16424 455

201. Penelope2.67641599.30.1818 33421 1575 544

64. Angelina2.68161603.90.1271 12536 3114 119

98. Ianthe2.68471606.70.1920 14852 3547 1532

34. Circe2.68641608.30.1073 14841 18446 527

123. Brunhilda2.69181613.20.1150 7257 30828 627

166. Rhodope2.69271613.90.2140 3051 12933 122

109. Felicitas2.69501616.00.3002 561 456 83

246. Asporina2.69941619.90.1065 25554 16235 1539

58. Concordia2.70041620.80.0426 18910 16120 52

103. Hera2.70141621.80.0803 3213 13618 524

54. Alexandra2.70951629.10.2000 29539 31345 1147

226. Weringia2.71181631.20.2048 28446 13518 1550

59. Olympia2.71241631.70.1189 1733 17026 837

146. Lucina2.71891637.50.0655 22734 8416 136

45. Eugenia2.72051639.00.0811 2325 14757 635

210. Isabella2.72351641.70.1220 4422 3258 518

187. Lamberta2.72721645.00.2391 2144 2213 1043

180. Garumna2.72861646.30.1722 12556 31442 054

160. Una2.72871646.40.0624 5557 922 351

140. Siwa2.73161649.00.2160 30033 1072 312

110. Lydia2.73271650.00.0770 33649 5710 60

185. Eunice2.73721654.10.1292 1632 15350 2317

203. Pompeia2.73761654.50.0588 4251 34837 313

200. Dynamene2.73781654.60.1335 4638 32526 656

197. Arete2.73901655.80.1621 32451 826 848

206. Hersilia2.73991656.50.0389 9544 14516 346

255. Oppavia2.74021656.60.0728 16915 146 933

247. Eukrate2.74121657.70.2387 5344 020 257

38. Leda2.74321659.60.1531 10120 29627 657

125. Liberatrix2.74371660.00.0798 27329 16935 438

173. Ino2.74461660.80.2047 1328 14834 1415

36. Atalanta2.74521661.30.3023 4244 35914 1842

128. Nemesis2.75141666.90.1257 1634 7631 616

93. Minerva2.75371669.00.1405 27444 54 837

127. Johanna2.75501670.30.0659 12237 3146 817

71. Niobe2.75581671.00.1732 22117 31630 2319

213. Lilæa2.75631671.40.1437 2814 12217 647

55. Pandora2.76041675.10.1429 1036 1056 714

237. Cœlestina2.76071675.50.0738 28249 8433 946

143. Adria2.76191676.60.0729 22227 33342 1130

82. Alcmene2.76201676.60.2228 13145 2657 251

116. Sirona2.76691681.10.1433 15247 6426 335

1. Ceres2.76731681.40.0763 14938 8047 1037

88. Thisbe2.76731681.50.1632 30834 27754 1611

215. Œnone2.76791682.00.0390 34624 2525 144

2. Pallas2.76801682.10.2408 12212 17245 3444

39. Lætitia2.76801682.10.1142 38 15715 1022

41. Daphne2.76881682.80.2674 22033 1798 1558

177. Irma2.76951683.50.2370 226 34917 127

148. Gallia2.77101684.80.1855 367 14513 2521

267. Tirza2.77421687.60.0986 2645 7359 62

74. Galatea2.77701690.30.2392 818 19751 40

205. Martha2.77711690.40.1752 2154 21212 1040

139. Juewa2.77931692.40.1773 16434 221 1057

28. Bellona2.77971692.70.1491 1241 14437 922

68. Leto2.78051693.50.1883 34514 451 758

216. Cleopatra2.79641708.00.2492 32815 21549 132

99. Dike2.79661708.30.2384 24036 4144 1353

236. Honoria2.79931710.70.1893 35659 18627 737

183. Istria2.80241713.40.3530 450 14246 2633

266. Aline2.80781718.50.1573 2352 23618 1320

188. Menippe2.82111730.70.2173 30938 24144 1121

167. Urda2.85331760.40.0340 2964 16628 211

81. Terpsichore2.85801764.80.2080 491 225 755

174. Phædra2.86001766.60.1492 25312 32849 129

243. Ida2.86101767.50.0419 7122 32621 110

242. Kriemhild2.86231768.70.1219 1231 20757 1117

129. Antigone2.86781773.90.2126 2424 13737 1210

217. Eudora2.86901774.90.3068 31441 16410 1019

158. Coronis2.87141777.20.0545 5656 28130 10

33. Polyhymnia2.87511780.70.3349 34259 919 156

195. Euryclea2.87901784.20.0471 11548 757 71

235. Caroline2.87951784.70.0595 26829 6635 94

47. Aglaia2.88191786.90.1317 31240 4020 51

208. Lachrymosa2.89261796.90.0149 12752 543 148

191. Kolga2.89671800.80.0876 2321 15947 1129

22. Calliope2.90901801.00.0193 6243 447 145

155. Scylla2.91271815.70.2559 821 4252 144

238. Hypatia2.91631819.00.0946 3218 18426 1228

231. Vindobona2.91921821.70.1537 25323 35249 510

16. Psyche2.92101823.40.1392 159 15036 34

179. Clytemnestra2.97111870.60.1133 35539 25313 747

239. Adrastea2.97361873.00.2279 261 18134 64

69. Hesperia2.97791877.00.1712 10819 18712 828

150. Nuwa2.97851877.50.1307 35527 20735 29

61. Danaë2.98551884.20.1615 3444 33411 1814

117. Lomia2.99071889.10.0229 4846 34939 1458

35. Leucothea2.99231890.60.2237 20225 35549 812

263. Dresda3.01201909.30.3051 30849 21756 127

221. Eos3.01341910.70.1028 33058 14235 1051

162. Laurentia3.02411920.80.1726 14552 3815 64

156. Xantippe3.03751933.70.2637 15558 24611 729

241. Germania3.03811934.00.1013 3407 27228 530

256. Walpurga3.04501940.80.1180 24017 18335 1244

211. Isolda3.04641942.20.1541 7412 26529 351

96. Ægle3.04971945.30.1405 16310 32250 167

257. Silesia3.05721952.50.2555 5416 3431 441

133. Cyrene3.05781953.00.1398 24713 3218 714

95. Arethusa3.07121965.90.1447 3258 24417 1254

202. Chryseis3.07771972.10.0959 12946 13747 848

268. ——3.08521973.90.1285 18448 12153 225

100. Hecate3.09041984.30.1639 3083 12812 623

49. Pales3.09081984.70.2330 3115 29040 38

223. Rosa3.09401987.90.1186 10248 490 159

52. Europa3.09551988.00.1098 10657 12940 727

245. Vera3.09851992.10.1950 2529 6237 510

86. Semele3.10151995.10.2193 2910 8745 447

159. Æmilia3.10892002.20.1034 10122 1359 64

48. Doris3.11272005.90.0649 7033 18455 631

196. Philomela3.11372006.80.0118 30919 7324 716

130. Electra3.11452007.70.2132 2034 1466 2257

212. Medea3.11572008.80.1013 5618 31516 416

120. Lachesis3.12112014.00.0475 2140 34251 71

181. Eucharis3.12262015.40.2205 9525 14445 1838

62. Erato3.12412016.90.1756 390 12546 212

222. Lucia3.12632019.00.1453 2582 8011 211

137. Melibœa3.12642019.10.2074 30758 20422 1322

165. Loreley3.12692019.60.0734 22350 3046 1012

251. Sophia3.13152024.10.1243 777 1576 1020

24. Themis3.13572028.10.1242 1448 3549 049

152. Atala3.13622028.60.0862 8423 4129 1212

10. Hygeia3.13662029.10.1156 2372 28538 349

259. Aletheia3.13692029.30.1176 24145 8832 1040

227. Philosophia3.13932031.60.2131 22623 33052 916

147. Protogenea3.13932031.60.0247 2538 25116 154

171. Ophelia3.14322035.40.1168 14359 10110 234

209. Dido3.14362035.90.0637 25733 20 715

31. Euphrosyne3.14682039.00.2228 9326 3131 2627

90. Antiope3.14752039.70.1645 30115 7129 217

104. Clymene3.15072042.70.1579 5932 4332 254

57. Mnemosyne3.15102043.00.1145 5325 2002 1512

250. Bettina3.15242044.30.1302 8728 2612 1254

252. Clementina3.15522047.10.0837 3558 20819 102

94. Aurora3.16022052.00.0827 4846 49 84

106. Dione3.16702058.60.1788 2557 6314 438

199. Byblis3.17772069.00.1687 26120 8952 1522

92. Undina3.18512076.30.1024 33127 10252 957

184. Deiopea3.18832079.40.0725 16922 33618 112

176. Idunna3.19062081.60.1641 2034 20113 2231

154. Bertha3.19762088.50.0788 19047 3735 2059

108. Hecuba3.21132101.00.1005 17349 35217 424

122. Gerda3.21772108.20.0415 20345 17843 136

168. Sibylla3.37652266.20.0707 1126 20947 433

225. Henrietta3.40072277.80.2661 29913 20045 2045

229. Adelinda3.41292302.90.1562 3327 3049 211

76. Freia3.41402304.10.1700 9049 2125 23

260. Huberta3.42122311.50.1113 31322 16848 618

65. Maximiliana3.42702317.20.1097 26036 15850 329

121. Hermione3.45352344.20.1255 35750 7646 736

87. Sylvia3.48332374.50.0922 33348 7549 1055

107. Camilla3.48472376.00.0756 11553 17618 954

175. Andromache3.50712399.00.3476 2930 2335 346

190. Ismene3.94712864.30.1634 10539 1770 67

153. Hilda3.95232869.90.1721 28547 22820 755