regions, 103; always accompanied 

 by a change of colour, 275. 



Seidel, his attempt to determine the 

 quantities of light of certain stars 

 of the 1st magnitude, 124. 



Self-luminous cosmical bodies, or 

 suns, 271. 



Seneca, on discovering new planets, 

 31. 



Simplicius, the Eclectic, contrasts 

 the centripetal and centrifugal 

 forces, 10; his vague view of gra- 

 vitation, 18. 



Sirius, its absolute intensity of 

 light, 127; historically proved to 

 have changed its colour, 177; its 

 association with the earliest de- 

 velopment of civilization in the 

 valley of the Nile, 179; etymolo- 

 gical researches concerning, 180. 



Smyth, Capt. W. H., calculations 

 of the orbits of double stars by, 

 287. 



Smyth, Piazzi, on the Milky Way, 

 199; on a Centauri, 252. 



Sothis, the Egyptian name of Sirius, 

 179. 



South, Sir James, observation of 

 380 double stars by, in conjunc- 

 tion with Sir John Herschel, 

 279. 



Southern constellations known to 

 Ptolemy, 185. 



Southern Cross, formerly visible on 

 the shores of the Baltic, 186. 



Southern hemisphere, in parts re- 

 markably deficient in constella- 

 tions, 151 ; distances of its stars, 

 first measured about the end of 

 the 16th century, 187. 



Space, conjectures regarding, 33 ; 

 compared to the mythic period of 

 history, 33; fallacy of attempts 

 at measurement of, 34; portions 

 between cosmical bodies not void, 

 36 ; its probable low tempera- 

 ture, 42. 



Spectra, the prismatic, 55; dif- 

 ference of the dark lines of, 

 according to their sources, 56. 



' ' Sphsera aplanes" of Macrobius, 3 1 . 



Spurious diameter of stars, 174. 



Star of the Magi, Ideler's explana- 

 tion of the, 208. 



Star of St. Catherine, 185. 



Star systems, partial, in which seve- 

 ral suns revolve about a common 

 centre of gravity, 277. 



Stars, division into wandering and 

 non-wandering, dates at least from 

 the early Greek period, 30; mag- 

 nitude and visibility of the, 60; 

 seen through shafts of chimneys, 

 73 ; undulation of the, 75 ; ob- 

 servation of, by daylight, 86 ; 

 scintillation of the, 96 ; variations 

 in its intensity, 101; the brightest 

 the earliest named, 119; rays of, 

 66, 171173; colour of, 175; 

 distribution of, 189; concentric 

 rings of, 201 ; variable, 218 ; 

 vanished, 221 ; periodically 

 changeable, 222 ; non-luminous, 

 of doubtful existence, 254 ; ratio 

 of coloured stars, 285. 



Steinheil's experiments on the velo- 

 city of the transmission of elec- 

 tricity, 116; his photometer, 124. 



Stellar clusters, or swarms, 189. 



Struve, on the velocity of light, 109 ; 

 his estimate of the number of the 

 fixed stars, 157; on the Milky 

 Way, 188; his Dorpat tables, 

 278 ; on the contrasted colours 

 of multiple stars, 282 ; calcula- 

 tion of the orbits of double stars 

 by, 287. 



Sun, the, described as " a perpetual 

 northern light," by Sir William 

 Herschel, 40 ; in intensity of 

 light, merely one of the fainter 

 fixed stars. 127; its place pro- 

 bably in a comparatively desert 

 region of the starry stratum, and 

 eccentric, 203. 



Suns, self-luminous cosmical bodies, 

 271. 



Table of photometric arrangement 

 of 190 fixed stars, 134; of 17 



