161 



MISCELLANEOUS INTELLIGENCE. 



§ 1. Mechanical Science. 



1. Eccentricity of Saturn's Ring. — " The most interesting cir- 

 cumstance in astronomy just now is the eccentricity of the Ring of 

 Saturn. M. Schwalz, of Dessau, first perceived it, and having 

 written of it to M. Harding, the latter believed that he also could 

 observe it. M. Harding informed me of the circumstance, and 1 

 also saw that which these two gentlemen had seen, as did likewise 

 my assistants. I nevertheless persisted in believing that it was an 

 optical illusion, occasioned by the shadow of the planet on the 

 ring, and therefore wrote to M. Struve to decide the point by means 

 of the superb micrometers attached to his great telescope. He had 

 the goodness to measure, on five different days, the distance of the 

 ring from the body of the planet, and he found, that what had been 

 observed was not merely an appearance, but that Saturn was really 

 eccentric with respect to his ring. You will see the details of these 

 observations in my Astronomische Nachrichten" &c. — Schumacher, 

 Bib. Univ. Juin, 1828. 



2. Resistance in Space to the Motion of Heavenly Bodies. — In an 

 account of the last appearance of Encke's comet in 1828, M. Gau- 

 tier states, that the results then obtained accorded with those which 

 Encke had previously procured, and which induced him, in 1823, 

 to suppose the existence of a medium or ethereal fluid in space, of 

 which the resistance, acting as a tangential force against the motion 

 of the comet, would augment the power of the sun, and shorten 

 the period of revolution. The most celebrated geometers, and even 

 Newton himself, had already calculated the influence which such a 

 resisting medium could exercise on the motions of comets and 

 planets. They had found that its effect would be to diminish con- 

 tinually the eccentricity of their orbits, and to shorten the longer 

 axes and the periods of their revolutions ; that the length of the 

 perihelium would suffer only a periodical change; and that the nodes 

 and the inclination of the orbit would not be altered. In the case 

 of Encke's comet, the two first effects have been decidedly produced, 

 and there are two circumstances to facilitate the calculation ; the 

 first is, that this comet is always seen in the same point of its orbit, 

 and near to its perihelium ; and the second, that its orbit is sub- 

 jected only to very slow alterations. Both these circumstances 

 permit the supposition that the times of revolution (at least for 

 some periods) diminish by an equal quantity, so that their dimi- 

 nution may be considered as proportional to the square of the 

 times ; the periodical variation of the perihelium may also be neg- 

 lected without inconvenience. M. Encke supposes, with Newton, 



JULY— SEPT., 1829. M 



