C 8 



of 1st magnitude, 137 ; of 

 tne variable stars, by Argelander, 

 232, and explanatory remarks, 

 233 240 ; of ascertained paral- 

 laxes, 262 ; of the elements of 

 the orbits of double stars, 289. 

 Telescope, the principle of, known 

 to the Arabs, and probably to the 

 Greeks and Romans, 53 ; disco- 

 veries by its means, 78 ; succes- 

 sive improvements of the, 80 ; 

 enormous focal length of some, 

 81 ; Lord Rosse's, 85 ; Bacon's 

 comparison of, to discovery ships, 

 175; penetrating power of the, 

 196. 



Telesio, Bernardino, of Cosenza, his 

 views of the phenomena of inert 

 matter, 16. 



Temperature, low, of celestial space, 



42 ; uncertainty of results yet 



obtained, 43 ; its influence on the 



climate of the earth, 45. 



Temporary stars, list of, 209 ; notes 



to, 210217. 

 Ternary stars, 286. 

 Timur Ulugh Beig, improvements 

 in practical astronomy in the 

 time of, 121. 



Translation in space of the whole 

 solar system, 265 ; first hinted 

 by Bradley, 265 ; verified by 

 actual observation by William 

 Herschel, 266 ; Argelander, 

 Struve, and Gauss's views, 266. 

 Trapezium in the great nebula of 

 Orion, investigated by Sir William 

 Herschel, 276. 



Tycho Brahe, his vivid description 

 of the appearance of a new star, 

 205 ; his theoiy of the formation 

 of such, 208. 



Uranological and telluric domain of 



the Cosmos, 29. 

 Uranus observed as a star by Flam- 



stead and others, 153. 



Vanished stars, 221 ; statements 

 about such to be received with 

 great caution, 221. 



Variable brightness of multiple and 

 double stars, 285. 



Variable stars, 218 ; mostly of a red 

 colour, 224 ; irregularity of their 

 periods, 226 j table of, 232. 



Velocity of light, 105 ; methods of 

 determining, 106 ; applied to the 

 determination of the parallax, 265. 



Visibility of objects, 70 ; how modi- 

 fied, 71. 



Vision, natural and telescopic, 51 ; 

 average natural, 60 ; remarkable 

 instances of acute natural, 66, 70. 



Wheatstone's experiments with re- 

 volving mirrors, 56 ; velocity of 

 electrical light determined by, 

 114. 



White Ox, name given to the nebula 

 now known as one of the Magel- 

 lanic clouds, 122. 



Wollaston's photometric researches, 

 127. 



Wright, of Durham, his view of the 

 origin of the form of the Milky 

 Way, 201. 



Yggdrasil, the world-tree of 

 Edda-Songs, 4, 5. 



the 



Zodiac, period of its introduction 

 into the Greek sphere, 160; its 

 origin among the Chaldeans, 161 ; 

 Ultimate mechanical cause " of all the Greeks borrowed from them 

 motion, unknown, 27. only the idea of the division, and 



Undulation of- the stars, 75. filled its signs with their own 



Undulations of rays ot light, various i catasterisms, 161 ; great antiquity 

 lengths of, 112. of the Indian very doubtful, 163. 



Unity of nature distinctly taught by Zodiacal light, Sir John Herschel OTJ 

 Aristotle, 1114. 



