218 INI 



Numerical results exceeding the grasp 

 of the comprehension, furnished alike 

 by the minutest organisms and the so- 

 called fixed stars, 30 ; encouraging views 

 on the subject, 31. 



Optical and physical double stars, 200; 

 often confounded, 200. 



Orbits of double stars, calculation of the, 

 211 ; their great eccentricity, 211 ; hy- 

 pothesis, that the brighter of the two 

 stars is at rest, and its companion re- 

 volves about it, probably correct, and a 

 great epoch in cosmical knowledge, 212. 



Orion, the six stars of the trapezium of 

 the nebula of, probably subject to pe- 

 culiar physical attraction, 210, 211. 



Pantschata or Pantschatra, the Indian the- 



ory of the five elements, 31. 

 Parallax, means of discovering the, point- 



ed out by Galileo, 183 ; number of par- 



allaxes hitherto discovered, 190 ; detail 



of nine of the best ascertained, 190. 

 Penetrating power of the telescope, 145, 



146. 



Periodically changeable stars, 164. 

 Periods within periods of variable stars, 



168 ; Argelander on, 168. 

 Peru, climate of, unfavorable to astronom- 



ical observations, 103. 

 Peters on parallax, 192. 

 Photometric relations of self-luminous 



bodies, 89 ; scale, 99. 

 Photometry yet in its infancy, 94 ; first 



numerical scale of, 94 ; Arago's meth- 



od, 96. 



Plato on ultimate principles, 12, 13. 

 Pleiades, one of the, invisible to the naked 



eye of ordinary visual power, 48 ; de- 



scribed, 141. 

 Pliny estimates the number of stars vis- 



ible in Italy at only 1600, 108. 

 Poisson, his view of the consolidation of 



the earth's strata, 36, 37. 

 Polarization of light, 45, 47. 

 Poles of greatest cold, 36. 

 Pouillet's estimate of the temperature of 



space, 36. 

 Prismatic spectra, 44 ; difference of the 



dark lines of, 45. 

 Ptolemy, his classification of the stars, 



90 ; southern constellations known to, 



137. 

 Pulkowa, number of multiple stars dis- 



covered at, 205, 206. 

 Pythagoreans, mathematical symbolism 



of tno, 12. 



Quaternary systems of stars, 210. 



Radiating heat, 35. 



Ratio of various colors among the mul- 



tiple and double stars, 209. 

 Rays of ftars, 52, 126-128 ; number of, in- 



dicate distances, 128; disappear when 



the star is viewed through a very sma 



aperture, 138, 129. 

 Red stars, 131 ; varia 



j Reflecting sextants applied to the determ- 

 I ination of the intensity of stellar light. 



1. 

 variable stars mostly red, 



Reflecting and refracting telescopes, 63. 

 i Regal stars of the ancients, 136. 

 j Resisting medium, proved by observa- 

 tions on Kncke's and other comets, 39. 

 Right ascension, distribution of stars ac- 

 cording to, by Schwinck, 140. 

 Rings, colored, measurement of the in- 

 tensity of light by, 96. 

 Rings, concentric, of stars, the hypothesis 

 of, favored by the most recent observa- 

 ! tions, 149. 

 i Rosse's, Lord, his great telescope, 65 ; it* 



services to astronomy, 66. 

 I Ruby-colored stars, 135. 



Saint Gall, the monk of, observed a new 

 j star distant from the Milky Way, 162. 



Saussure asserts that stars may be seen 

 in daylight on the Alps, 57 ; the asser- 

 tion not supported by other travelers' 

 j experience, 58. 



Savary, on the application of the aberra- 

 tion of light to the determination of the 

 parallaxes, 194 ; an early calculator of 

 the orbits of double stars, 211. 



Schlegel, A. W. von, probably mistaken 

 as to the high antiquity of the Indian 

 zodiacs, 121 



Schwinck, distribution of the fixed stars 

 in his " Mappa coslestis," 140. 



Scintillation of the stars, 73 ; variations 

 in its intensity, 76 ; mentioned in the 

 Chinese records, 77 ; little observed in 

 tropical regions, 77, 78 ; always accom- 

 panied by a change of color, 202. 



Seidel, his attempt to determine the quan- 

 tities of light of certain stars of the first 

 magnitude, 93. 



Self-luminous cosmical bodies, or suns, 

 199. 



Seneca, on discovering new planets, 28. 



Simplicius, the Eclectic, contrasts the cen- 

 tripetal and centrifugal forces, 12 ; his 

 vague view of gravitation, 18. 



Sirius, its absolute intensity of light, 95 ; 

 historically proved to have changed its 

 color, 131 ; its association with the ear- 

 liest development of civilization in the 

 valley of the Nile, 133 ; etymological re- 

 searches concerning, 133, 134. 



Smyth, Capt W. H., calculations of the 

 orbits of double stars by, 211. 



Smyth, Piazzi, on the Milky Way, 146, 

 147 ; on a Centauri, 185. 



Sothis, the Egyptian name of Sirius, 133, 



South, Sir James, observation of 380 dou- 

 ble stars by, in conjunction with Sir 

 John Herschel, 205. 



Southern constellations known to Ptol- 

 emy, 137. 



Southern Cross, formerly visible on the 

 shores of the Baltic-, 138. 



Southern hemisphere, in parts remark- 

 ably deficient in constellations, 112; dis- 

 tances of its stars, first measured about 

 the end of the sixteenth century, 138. 



