Cosmical vapor, question as to condensa- 

 tion of, 37 ; Tycho Brahe's and Sir Will- 

 iam Herschel's theories, 154. 



" Cosmos," a pseudo-Aristotelian work, 

 16. 



Crystal vault of heaven, date of the desig- 

 nation, 133 ; its signification according 

 to Empedocles, 123 ; the idea favored 

 by the Fathers of the Church, 125. 



Cyanometer, Arago's, 97. 



Dark cosmical bodies, question of, 164, 

 187. 



Dolambrc on the velocity of light, 82. 



Descartes, his cosmical views, 19, 20 ; sup- 

 presses his work from deference to the 

 Inquisition, 20. 



Dioptric tubes, the precursors of the tele- 

 scope, 43. 



Direct and reflected light, 45. 



Distribution of the fixed stars, according 

 to right ascension, 140. 



Dorpat Table (Struve's) of multiple stars, 

 205. 



Double stars, the name too indiscrimin- 

 ately applied, 199, 200 ; distribution into 

 optical and physical. 200 ; pointed out 

 by Galileo as useful in determining the 

 parallax, 200 ; vast increase in their ob- 

 served number, 201, 205; those earliest 

 described, 201; number in which a 

 change of position has been proved, 

 206 ; greater number of double stars in 

 the northern than in the southern hem- 

 isphere, 207 ; occurrence of contrasted 

 colors, 207 ; calculation of their orbits, 

 211 ; table of the elements, 213. 



Earth-animal, Kepler and Fludd's fancies 



regarding the, 19. 

 Edda-Songs, allusion to, 8. 

 Egypt, zodiacal constellations of, their 



date, 121. 

 Egyptian calendar, period of the complete 



arrangement of the, 133. 

 Ehrenberg on the incalculable number 



of animal organisms, 30. 

 Electrical light, velocity of transmission 



of, 86. 

 Electricity, transmission of, through the 



Elements, Indian origin of the hypothesis 

 of four or five, 11. 



Emanations from the head of some com- 

 ets, 39. 



Encke, his accurate calculation of the 

 equivalent of an equatorial degree, 81 ; 

 on the star-maps of the Berlin Academy, 

 116 ; an early calculator of the orbits 

 of double stars, 2C \ ; his theory of their 

 motion, 212. 



Encke's comet, considerations on space, 

 derived from periods of revolution of, 

 27; a resisting medium proved from 

 observation on, 39. 



Ether, different meanings of, in the East 

 and the West, 31, 32. 



Ether (Ak so, in Sanscrit), one of the In- 

 dian five elements, 31. 



Ether, the, fiery, 35. 



Euler's comparative estimate of the light 

 f the sun and moon, 95. 



Fixed stars, the term erroneous, 27, 122 ; 

 scintillation of the, 73 ; variations in its 

 intensity, 76 ; our sun one of the fainter 

 fixed stars, 95; photometric arrange- 

 ment of, 99 ; their number, 105 ; num- 

 ber visible at Berlin with the naked eye, 

 107; at Alexandria, 107; Struve and 

 Herschel's estimates, 116; grouping of 

 the, 117 ; distribution of the, 140 ; prop- 

 er motion of the, 182 ; parallax, 188 ; 

 number of, in which proper motion has 

 been discovered, greater than of those 

 in which change of position has been 

 observed, 206, 207. 



Fizeau, M., his experiments on the veloc- 



ity of light, 80, 83. 

 Formula for 



computing variation of light 

 of a star, by Argelander, : 



Galactic circle, average number of stars 

 in, and beyond the, 139. 



Galileo indicates the means of discover- 

 ing the parallax, 188. 



Galle, Dr., on Jupiter's satellites, 50 ; on 

 the photometric arrangement of the 

 fixed stars, 99. 



Garnet star, the, a star in Cepheus, so 

 called by William Hcrschel, 1G6. 



Gascoigne applies micrometer threads to 

 the telescope, 42. 



Gauging the heavens, by Sir William Her- 

 schel, 138, 139 ; length of time neces- 

 sary to complete the process, 139. 



Gauss, on the point of translation in space 

 of the whole solar system, 196. 



Gilliss, Lieutenant, on the change of color 

 of the star ij Argus, 135. 



Gravitation, not an essential property of 

 bodies, but the result of some higher 

 and still unknown power, 22, 23. 



Greek sphere, date of the, 119, 121. 



Green and blue suns, 208. 



Groups of fixed stars, recognized even 

 by the rudest nations, 117 ; usually the 

 same groups, as the Pleiades, the Great 

 Bear, the Southern Cross, &c., 117, 118. 



Halley asserted the motion of Sinus and 

 other fixed stars, 26, 27. 



Hassenfratz, his description of the rays 

 of stars as caustics on the crystalline 

 lens, 52, 127. 



Heat, radiating, 35. 



Hepidannus, monk of Saint Gall, a new 

 star recorded by, 157, 162. 



Herschel, Sir William, on the vivifying 

 action of the sun's rays, 34 ; his estimate 

 of the number of the fixed stars, 116, 

 117 ; his " gauging the heavens," and its 

 result, 138, 139. 



Herschel, Sir John, on the transmission 

 of light, 30 ; on the influence of the sun'g 

 rays, 34 ; compares the sun to a per- 

 petual northern light, 34 ; on the at- 

 mosphere, 37 ; on the blackness of the 

 ground of the. heavens, 39 ; on stars 

 seen in daylight^ 57; on photometry. 



