OF CONTEXTS. ll 



Saturn; bands, rings, eccentric position, pp. 517 522. 



Satellites of Saturn, pp. 523524. 

 Vranvs, pp. 524526. 



Satellites of Uranus, pp. 526 .127: 

 Neptune: discovery and elements, pp. 527 530. 



Satellites of Neptune, pp. 531532. 



III. The Comets: with the smallest masses occupying immense spaces ; 

 configuration ; periods of revolution ; separation ; elements of the interior 

 comets, pp. 533 560. 



IV. The ring of the zodiacal light : Historical particulars. Intermit- 

 tence two-fold ; hourly and annual ? Distinction to be made between 

 the cosmical luminous process which belongs to the zodiacal light itself 

 and the variable transparency of our atmosphere. Importance of a long 

 series of corresponding observations under the tropics at different eleva- 

 tions above the sea from 9 to 12,000 feet. Reflection like that at sunset. 

 Comparison in the same night with certain parts of the Milky Way. 

 Question as to whether the zodiacal light coincides with the plane of the 

 Sun's equator, pp. 561 565. 



V. Shooting stars, fire-balls, meteoric-stones : Oldest positively deter- 

 mined fall of aerolites, and the influence which the fall at ^Egos Potamos 

 and its cosmical explanations exercised upon the theories of the universe 

 of Anaxagoras and Diogenes of Apollonia (of the later Ionic school) ; 

 force of revolution which counteracts the power of the fall (centrifugal 

 force and gravitation), pp. 566 572 (notes 5-9). Geometric and physical 

 relations of meteors in sporadic and periodic falls ; divergence of the 

 shooting-stars ; definite points of departure; mean number of sporadic 

 and periodic shooting- stars in an hour in different months, pp. 572 579, 

 notes 13 14. Besides the stream of St. Laurentius, and the now more 

 feeble November phenomenon, four or five other falls of shooting-stars 

 have been discovered which very probably occur periodically during the 

 year, p. 579, notes 20 21. Height and velocity of the meteors, p. 583. 

 Physical relations, colour and tails, process of combination, magnitudes; 

 instances of the firing of buildings, p. 583. Meteoric stones ; falls of 

 aerolites when the sky is clear, or after the formation of a small dark 

 meteoric cloud, p. 587, notes 25 and 26. Problematical abundance of the 

 shooting-stars between midnight and the early hours of morning (hourly 

 variations), p. 590. Chemical relations of the aerolites ; analogies with 

 the constituents of telluric rock, pp. 592 596. 



Conclusion: Retrospect of the undertaking. Limitation consistent 

 with the nature of a physical description of the universe. Representation 

 of the actual relations of cosmical bodies to each other. Kepler's laws 

 of planetary motion. Simplicity of the Uranological problem in opposi- 

 tion to the telluric, on account of the exclusion of material heterogeneity 

 and change. Elements of the stability of the planetary system, pp. 597 

 601. 



