TV. Astronomy. 



1. Neto Planet.— The discovery of another planet by Herr 

 Knorre was announced by telegram to Prof. Henry, Jan. 11th. 



2. Harvard Observatory Engravings. — The last instalments of 

 the engravings from Harvard College Observatory have been dis- 

 tributed to the subscribers. Instead of 30 plates as promised, 35 

 have been issued. These later plates represent two star clusters, 

 six views of nebulae, four views of Donati's comet, and three of 

 Coggia's comet. A letter press description of the engravings is, 

 we understand, to be soon issued. 



3. The Uranian and Neptunian Systems investigated with the 

 2%-inch Equatorial of the U. S. N\ Observatory; by Professor 

 Newcomb. Appendix I of the Wash. Obs. for 1873, p. 74.— 

 This paper is the first extended contribution of results obtained by 

 the large Washington telescope. It is a discussion of the observa- 

 tions made between November, 1873, and May, 1875, upon the 

 four satellites of Uranus, and the satellite of Neptune. It closes 

 with tables of the motions of the satellites, for a portion of which 

 credit is given to Prof. Holden. 



Prof. Newcomb obtains ^^^^y^j as the most probable value of the 

 mass of Uranus, with an estimated probable error of the denom- 

 mator of lOO. He finds no evidence of any mutual inclination of 

 the orbits of the four satellites and but slight evidence of any 

 real eccentricity. The following are the mean distances from 

 Uranns at the mean distance of Uranus from the sun: Ariel, 

 13'-78; Umbriel, W-2Q; Titania, 3l"-48; and Oberon, 42'-10. 

 The periods of revolution are 2'^'520378; 4''-144537; 8''-705897, 

 and 13'i-463260. The former two are not changed from the deter- 

 minations of Lassell and Marth. The inclination of the plane to 

 the ecliptic is 97°-85— 0-013T, counting from the epoch 1850. 



The only means of estimating the masses of the satellites is a com- 

 parison of their light with that of the planet. From this Pro£ 

 Newcomb infers that they probably do not exceed ys^j^Tr ^* ^^^ 

 planet. If so their mutual action, and the sun's action on them, 



the planet, and outside of Oberon, having one-third the brilliancy 

 of the latter, and therefore that none of Sir William Ilerschel's 

 supposed outer satellites can have any real existence. The dis- 

 tances of the four known satellites increase in so regular a way 

 that It can hardly be supposed that any others exist betweeii 

 them. Of what may be inside of Ariel, it is impossible to speak 

 with certainty, since, in the state of atmosphere which prevails 

 during our winter, all the satellites would disappear at 10" dis- 

 tance from the planet. The planet always presented itself of a 

 sea-green color. No variations of tint were ever seen. Markings 

 on the planet were not especially looked for, but had any been 

 visible they could hardly have escaped notice." 



For the mass of Neptune the value t^^^tt is obtained. In the 



