ASTRONOMY. 163 



oiul satellite. Its albedo proves to be so high that it is capable of pre- 

 servini;' its biilliancy tiiroiifihont the entire transit. 



Tlie third and tiist satellites evidently possess sides of different al- 

 bedo, one high enough to maintain a brighter aspect than the other, or 

 even, as in the case of the third, to make itappear white when one side 

 is i)resented to the earth and dark when the otlier. Finally, to (piote 

 from the original pa[)er, '' it is not unreasonabhi to (tonclude tliat these 

 anomalous phenomena are due to functional idiosyncrasies in the eye 

 itself, rather than to physical peculiarities of the Jovian system." 



Mr. Denning has obtained from observations of the red spot made 

 between February 12 and August 22, 1888, a rotation of ()'' 55'" 4()'^.21, 

 nearly one second less than the spot gave in 1885-80, though six sec- 

 onds greater than in 1879. 



The value obtained for the mass of Jupiter by von Haerdtl in his dis- 

 cussion of Winnecke's comet is 1 : 1017.152 i 0.0130. 



Satitkn. — The (irst number of a new series of publications called 

 Supplements to the Pulkowai Observations contains an interesting me- 

 moir by Dr. Hermann Struve on the outer satellites of Saturn. lie dis- 

 cusses his own observations made with the 15-inch refractor in the 

 years 1884-1880 on Iai)etus, Titan, Ithea, and Dione, with a view to 

 correcting the elements of these satellites, and also the values of the 

 nuiss and ellipticity of Saturn. The mass of Saturn was found by Bes- 

 sel to be 1 : 3501. Oi 0.77, or with a slight correction indicated in the pres- 

 ent paper, 1 : 3502.5. Prof. Asaph llall, on the other If^nd, obtained tiie 

 value 1 : 3181.3 i 0.51. Struve considers the rather large discordance b»'- 

 tweeu these values due to systematic error in measuring the distance 

 of a satellite from a limb, and his own observations consist entirely of 

 comparisons of one satellite with another, either by differences of right 

 ascension and north polar distance or of distance and position angle. 

 His resulting value of the mass of Saturn agrees closely with Ilessel's, 

 being 1:3108. The correction of the elements has been carefully and 

 laboriously carried out by the method of least s(iuares. ( The Obnerva- 

 tory, 11 :.303, July, 1888.) 



Mr. G. W. ndl,in Iiis paper on the motion of Hyperion and the u:ass 

 of Titan, has ol>tained for the latter 1 : 1711, Saturn's mass being unity. 

 Newcomb's corrected value, and Ormond Stone's \alue, accord well with 

 this. 



Uranus. — Dr. Valentiner, of the Karlsruhe Observatory, and his as- 

 sistant. Dr. von Kebeur-J'aschwitz, were able to detect in April, 1887, a 

 slight ellipticity in the disk of the i)lanet Uranus, but their instrument, 

 a O-inch e([uatorial, was not of suflicient i)ower to make satisfactoiy 

 measures. 



Nep'Ittne. — Tisseraiid has shown that the i)rogressive (;hanges in tll(^ 

 node and iiu-lination of the orbii of the satellite of Neptune, can be ex- 

 plained by supposing a slight llntleiiing of the surface of the planet; 

 but the flattening would probably he too slight to be measured. Fur- 



