CHAPTER XII.

HERSCHEL (FROM 1738 A.D. TO 1822 A.D.), §§ 251-271 323-353

§§ 251-2. William Herschel’s early career: Bath: his first telescope 323

§§ 253-4. The discovery of the planet Uranus, and its consequences: Herschel’s removal to Slough 325

§ 255. Telescope-making: marriage: the forty-foot telescope: discoveries of satellites of Saturn and of Uranus 327

§ 256. Life and work at Slough: last years: Caroline Herschel 328

§ 257. Herschel’s astronomical programme: the study of the fixed stars 330

§ 258. The distribution of the stars in space: star-gauging: the “grindstone” theory of the universe: defects of the fundamental assumption: its partial withdrawal. Employment of brightness as a test of nearness: measurement of brightness: “space-penetrating” power of a telescope 332

§ 259. Nebulae and star clusters: Herschel’s great catalogues 336

§ 260. Relation of nebulae to star clusters: the “island universe” theory of nebulae: the “shining fluid” theory: distribution of nebulae 337

§ 261. Condensation of nebulae into clusters and stars 339

§ 262. The irresolvability of the Milky Way 340

§ 263. Double stars: their proposed employment for finding parallax: catalogues: probable connection between members of a pair 341

§ 264. Discoveries of the revolution of double stars: binary stars: their uselessness for parallax 343

§ 265. The motion of the sun in space: the various positions suggested for the apex 344

§ 266. Variable stars: Mira and Algol: catalogues of comparative brightness: method of sequences: variability of α Herculis 346

§ 267. Herschel’s work on the solar system: new satellites: observations of Saturn, Jupiter, Venus, and Mars 348

§ 268. Observations of the sun: Wilson: theory of the structure of the sun 350

§ 269. Suggested variability of the sun 351

§ 270. Other researches 352

§ 271. Comparison of Herschel with his contemporaries: Schroeter 352