OP CONTENTS. Vll 



i,lusters of stars ? — p. 13 (note $, p. 22, and p. 23, note *). Histcncal 

 particulars — p. 14 (note *, p. 28). Number of nebulae whose positions 

 are determined — p. 26 (notes * and +). Distribution of nebula; and 

 clusters of stars in the northern and southern hemispheres — p. 27 ; 

 spaces poor in nebulae, and the maxima of accumulation — p. 28, and 

 note *. Configuration of nebulae : spherical, annular, spiral, and plan- 

 etary nebulae— p. 31. Nebula (cluster of stars) in Andromeda — p. 16- 

 31 (note t, p. 31); nebula in Orion's sword — p. 17-39 (notes *, p. 18, 

 t, p. 23 $, p. 36, *, p. 38, $, p. 39, and *, p. 40) ; large nebula round t] 

 Argfis — p, 40 ; nebula in Sagittarius — p. 41 ; nebula in Cygnus and Vul- 

 pes ; spiral nebula in the northern Canes Venatici — p. 41. The two Ma- 

 gellanic Clouds — p. 43 (note *, p. 48). Black spots or Coal-sacks — p. 51. 



j3. The Solar region ; planets and their moons, ring of the zodiacal 

 light, and swarms of meteor-asteroids — p. 53-88. 



I. The Sun considered as a central body : Numerical data — p. 59 (note 

 *, p. 59, and p. 62, note *). Physical constitution of the surface; en- 

 velopes of the dark solar globe ; Sun-spots, faculae — p.-61. Diminutions 

 ia the daylight recorded by the annalists ; problematic obscurations— 

 p. 73, and note. Intensity of the light in the center and at the edge 

 of the Sun's disk — p. 79, and note; also p. 81, note *. Correlation of 

 light, heat, electricity, and magnetism; Seebeck, Ampere, Faraday— 

 p^Si. Influence of the Sun's spots upon the temperature of our at- 

 mosphere — p. 80. 



IT. The Planets : ' 



A. General comparative considerations : 



a. Principal Planets : 



1. Number and epoch of discovery — p. 89. Names, planetary 

 days (week), and planetary hours — p. 92, and note t; also 

 p. 94, note *. 



2. Classification of the planets in two groups^-p. 102. 



3. Absolute and apparent magnitudes; configuration — p. 105. 



4. Order of the planets and their distances from the Sun; the 

 so-called law of Titius; old belief that the cosmical bodies 

 which we now see were not all visible from the beginning ; 

 Proselenes — p. 106, note *, p. 108, and p. 120, note *. 



5. Masses of the planets — p. 118. 



6. Densities of the planets — p. 119. 



7. Penods of sidereal revolution and axial rotation — p. 120. 



8. Inclination of the planetary orbits and axes of rotation ; 

 their influence njion climate — p. 121, and note t, p- 126. 



h. Secondary planets — p. 127 



B. Special consideration ; enumeration of the individual planets anrJ 

 their relation to the Sun as central body. 



The Sun—p. 135-137. 



Mercury— p. 137, 138. 



Venus; spots— p. 138-141. 



The Earth; numerical relations — p. 141. 



