560 ADDITIONS. 



These discoveries have been distributed among the observatories of 

 Europe. The bright sky of Naples has revealed seven new planets to 

 the telescope of Signor Gasparis. Marseilles has given us one ; Ger- 

 many, four, discovered by M. Luther at Bilk; Paris has furnished 

 seven ; and Mr. Hind, in Mr. Bishop's private observatory in London, 

 notwithstanding our turbid skies, has discovered no less than ten plan- 

 ets ; and there also Mr. Marth discovered (^) Amphitrite. Mr. Gra- 

 ham, at the private observatory of Mr. Cooper, in Ireland, discovered 

 |P Metis. 



America has supplied its planet, namely (sjjj) Euphrosyne, discovered 

 by Mr. Ferguson at Washington ; and the most recent of these discov- 

 eries is that by Mr. Pogson, of Oxford, who has found the forty-second 

 of these Minor Planets, which has been named Isis. 5 



I may add that it appears to follow from the best calculations that 

 the total mass of all these bodies is very small. Herschel reckoned 

 the diameters of Ceres at 35, and of Pallas at 26 miles. It has since 

 been calculated 6 that some of them are smaller still ; Victoria having 

 a diameter of 9 miles, Lutetia of 8, and Atalanta of little more than 4. 

 It follows from this that the whole mass would probably be less than 

 the sixth part of our moon. Hence their perturbing effects on each 

 other or on other planets are null ; but they are not the less disturbed 

 by the action of the other planets, and especially of Jupiter. 



Anomalies in the Action of Gravitation. 



The complete and exact manner in which the doctrine of gravitation 

 explains the motions of the Comets as -well as of the Planets, has made 

 astronomers very bold in proposing hypotheses to account for any de- 

 \ ? iations from the motion which the theory requires. Thus Encke's 

 Comet is found to have its motion accelerated by about one-eighth of 

 a day in every revolution. This result was conceived to be established 

 by former observations, and is confirmed by the facts of the appearance 

 of 1852. 1 The hypothesis which is proposed in order to explain this 

 result is, that the Comet moves in a resisting medium, which makes it 

 fall inwards from its path, towards the Sun, and thus, by narrowing 

 its orbit, diminishes its periodic time. On the other hand, M. Le Ver- 

 rier has found that Mercury's mean motion has gone on diminishing; 



5 I take this list from a Memoir of M. Erulms, Berlin, 1856. 



6 Brulins, as above. 7 Berlin Memoirs, 1SG4. 



