Pantschata, or Pantschatra, the 

 Indian theory of the five elements, 

 36. 



Parallax, means of discovering the, 

 pointed out by Galileo, 256; 

 number of parallaxes hitherto 

 discovered, 258; detail of nine 

 of the best ascertained, 259. 



Penetrating power of the telescope, 

 196. 



Periodically changeable stars, 222. 



Periods within periods of varia- 

 able stars, 228; Argelander on, 

 228. 



Peru, climate of, unfavourable to 

 astronomical observations, 139. 



Peters, on parallax, 261. 



Photometric relations of self-lumi- 

 nous bodies, 119; scale, 132. 



Photometry, yet in its infancy, 125; 

 first numerical scale of, 126; 

 Arago's method, 128. 



Plato, on ultimate principles, 11. 



Pleiades, one of the, invisible to the 

 naked eye of ordinary visual 

 power, 60; described, 191. 



Pliny estimates the number of stars 

 visible in Italy at only 1600, 

 145. 



Poisson, his view of the consolida- 

 tion of the earth's strata, 44. 



Polarisation of light, 57 60. 



Poles of greatest cold, 43. 



Pouillet's estimate of the tempe- 

 rature of space, 43. 



Prismatic spectra, 55; difference of 

 the dark lines of, 56. 



Ptolemy, his classification of the 

 stars, 120; southern constella- 

 tions known to, 185. 



Pulkowa, number of multiple stars 

 discovered at, 279. 



Pythagoreans, mathematical sym- 

 bolism of the, 10. 



Quaternary systems of stars, 286. 



Radiating heat, 41. 

 Ratio of various colours among the 

 multiple and double stars, 285. 



Rays of stars, 66, 171 ; number of, 

 indicate distances, 173; disappear 

 when the star is viewed through a 

 very small aperture, 173. 



Red stars, 176 ; variable stars mostly 

 red, 224. 



Reflecting sextants applied to the 

 determination of the intensity of 

 stellar light, 123. 



Reflecting and refracting telescopes, 

 82. 



Regal stars of the ancients, 184. 



Resisting medium, proved by obser- 

 vations on Encke's and other 

 comets, 47. 



Right ascension, distribution of 

 stars according to, by Schwinck, 

 189. 



Rings, coloured, measurement of 

 the intensity of light by, 128. 



Rings, concentric, of stars, the hy- 

 pothesis of, favoured by the most 

 recent observations, 201. 



Rosse's, Lord, his great telescope, 

 85 ; its services to astronomy, 85. 



Ruby-coloured stars, 183. 



Saint Gall, the monk of, observed 

 a new star distant from the 

 Milky Way, 220. 



Saussure asserts that stars may be 

 seen in daylight on the Alps, 74 ; 

 the assertion not supported by 

 other travellers' experience, 75. 



Savary, on the application of the 

 aberration of light to the deter- 

 mination of the parallaxes, 264 ; 

 an early calculator of the orbits 

 of double stars, 287. 



Schlegel, A. W. von, probably mis- 

 taken as to the high antiquity of 

 the Indian zodiacs, 163. 



Schwinck, distribution of the fixed 

 stars in his " Mappa ccelestis," 

 189. 



Scintillation of the stars, 96 ; varia- 

 tions in its intensity, 101 ; men- 

 tioned in the Chinese records, 

 103; little observed in tropical 



