34 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



complete integration of these four equations is effected by 

 liim by the use of elliptic integrals and the so-called theta 

 function. 



THE UKANIAN AND NEPTUNIAN SYSTEMS. 



No sooner was the 26-inch refractor at Washington in work- 

 ing order than its powers were tested by an examination of 

 the planets Uranus and Neptune, in order to ascertain how 

 well the satellites of those planets were visible by its means. 

 The two nearest satellites of Uranus had never been recog- 

 nized as such by any astronomer until Lassell's telescope 

 was mounted at Malta, nor again after that until they were 

 observed at Washington. The results of the first year's ob- 

 servations of these satellites are now published in a memoir 

 by Professor Simon Newcomb on the Uranian and Neptuni- 

 an systems, accompanied by tables whereby the apparent 

 positions of the satellites may in a few minutes be predicted 

 Avith sufficient accuracy. Apart from the determination of 

 the exact positions and movements of the satellites them- 

 selves, Professor Newcomb's memoir finds its highest interest 

 in the fact that he deduces from these observations new de- 

 terminations of the masses of the two principal planets. His 

 results have an intrinsic accuracy far surpassing that of the 

 very discordant results given by previous observers, and his 

 long series of unprecedentedly exact observations (although 

 the objects observed by him are justly considered the most 

 difficult that offer themselves to the astronomer) is a fine 

 testimony to the correctness of the principle adopted by 

 him that, " in the present state of astronomy, it is better to 

 do one thing well than many things indifferently." 



Among the more important results. Professor Newcomb 

 states that we are led to the remarkable conclusion that the 

 eccentricities of the satellites of the two outer planets are in- 

 sensible so far as they can be determined from all the obser- 

 vations hitherto made on them, and that in the case of Obe- 

 ron and Titania the orbits are more nearly circular than in 

 the case of any of the large planets of our system. The 

 most probable value of the mass of Uranus is, he concludes, 

 ^_^^_^ with a probable error of 100 in the denominator. For 

 Neptune, Professor Newcomb finds that the mass is yg-g-Fo-) 

 with a probable error of 70 in the denominator. He adds 



