SIDEREAL ASTRONOMY. 349 



and in accordance with the true interests and legitimate 

 course of physical enquiry. 



Our author discusses these subjects with his wonted ability ; 

 and also the collateral questions as to the existence of non- 

 luminous bodies in space (an opinion confidently held by 

 several eminent astronomers) ; and the possible, or probable, 

 loss of light in a certain ratio to the length of line it traverses 

 through the heavens, as inferred by Struve from some of his 

 recent researches.* These loftier but less certain specula- 

 tions of the Stellar Astronomy are followed by a series of 

 chapters on our own Solar system ; including the Sun, the 

 planets and their satellites, comets, the ring of zodiacal light, 

 and meteoric asteroids. This part of Humboldt's work is 

 admirably executed ; lucid in arrangement, ample in details, 

 and suggestive throughout of those great relations and induc- 

 tions which form the true philosophy of every science. The 

 deficiencies are such as belong chiefly to the date of publica- 

 tion, recent though this is. The number of the small planets 

 recognised between Mars and Jupiter has been nearly quad- 

 rupled since Humboldt's first record of them. A third or 

 inner ring of Saturn has lately been discovered ; while the 

 conjoint researches of Struve and Bond (the latter an observer 

 of whom America may justly be proud) give some reason to 

 believe that the whole annular system of Saturn has, since 

 the time of Huyghens, been approaching nearer to the body 

 of the planet, and cannot therefore be considered in the state 

 of stable equilibrium which Laplace had supposed. The two 

 new satellites of Uranus, discovered by Lassell in October, 

 1851, were unknown when this volume of the Cosmos was 

 printed, but are noticed in an appendix to it. In the Chapter 



* Etudes d'Astronomie Stellaire, 1847; in which work all these profound 

 questions find their place. Struve entertains the belief that some of the 

 anomalies of present calculation could be reconciled by supposing a loss of one 

 per cent, of light, in passing through a distance, equal to that of an average star 

 of the first magnitude ; thus modifying in a certain degree the law of diminu- 

 tion in the inverse ratio of distance. 



