VI GENERAL SUMMARY 



Explanation of the sparkling and scintillation of the stars p. 73. Ve- 

 locity of light p. 79-88. Order of magnitude of the stars; photomet- 

 ric relations and methods of measurement p. 89-98. Cyanometer 

 p. 97. Photometric order of the fixed stars p. 99-102. 



III. Number, distribution, and color of the fixed stars ; Stellar clusters 

 and the Milky Way: States of the sky which hinder or favor the de- 

 tection of stars p. 103. Number of the stars ; how many may be seen 

 with the naked eye p. 104. How many have been inserted in stellar 

 charts with determinations of position p. 108. Conjectural estimation 

 of the number of stars which can be visible in the entire heavens with 

 our present powers of penetrating space p. 105. Contemplative as- 

 trognosy of uncivilized people p. 109. The Grecian sphere p. 118. 

 The crystal sky p. 123. False diameter of the fixed stars in telescopes 

 p. 129. Smallest objects in the heavens which have yet been seen 

 p. 130. Difference of colors in the stars, and the changes which have 

 taken place in the colors since antiquity p. 130. Sinus (Sethis') p. 

 132. The four royal stars p. 136. Gradual acquaintance with the 

 Southern heaven p. 137. Distribution of the fixed stnrs, laws of rela- 

 tive accumulation, gauging p. 138. Clusters and swarms of stars p. 

 140. The Milky Way p. 143. 



IV. Stars that have neicly appeared and disappeared ; variable stars 

 and changes in the intensity of their light whose periodicity has not been 

 investigated: New stars in the last 2000 years p. 151. Periodically 

 changeable stars: Historical particulars p* 151. Color p. 165. Num- 

 ber p. 164. Order recognizable in apparent irregularity; great dif- 

 ferences of brightness ; periods within periods p. 167. Argelander's 

 table of the variable stars with commentary p. 172. Variable stars 

 in undetermined periods (q Argfis, Capella, stars of the Ursae Major and 

 Minor) p. 181. Reference to the possible changes of temperature on 

 the Earth's surface p. 181. 



V. Proper motion of the fixed stars, dark coamical bodies, parallax; 

 doubts as to the assumption of a central body for the entire heaven of fixed 

 stars : Change of the physiognomy of the sky p. 18ii. Amount of the 

 proper motion p. 184. Evidence in favor of the probable existence 

 of non-luminous bodies p. 186. Parallax and measurement of the dis- 

 tance of some fixed stars from our solar system p. 187. The aberra- 

 tion of light may be applied to the determination of the parallax of 

 double stars p. 194. The discovery of the proper motion of the fixed 

 stars has led to the knowledge of the motion of our own solar system, 

 and even to the knowledge of the direction of this motion p. 184 and 

 194. Problem of the situation of the center of gravity of the whole 

 heaven of fixed stars and central suns? p. 196, and note t, p. 198, and 

 p. 199, note *. 



VI. Double stars, period of revolution of two suns round a common 

 center of gravity : Optical and physical double stars p. 200; number 

 p. 201. Uniformity and difference of color; the latter not the conse- 

 quence of optical deception, of the contrast of complementary colors 

 p. 207, note *, p. 206, and p. 209, note *. Change of brightness p. 209. 

 Multiple combinations (three to six fold) p. 209. Calculated orbitual 

 elements, half major axis and period of rotation in years p. 213. 



VII. Nebula, Magellanic Clouds, and Coal-sacks: Resolvability of tho 

 nebula?; questions as to whether they are all remote and crowded 



