ASTKONOMY. 139 



Tisseraud finds that iiis results agree closely with the facts of observa- 

 tiou, the computed rate of retrograde motiou of the perisaturuium of 

 HyperioD being IS^.S per annum, whilst the observed quantity is 20°, 

 and he also finds that his value of the mass of Titan (yoTso) <liffers little 

 from that obtained by Newcomb. (Observatory, November, 1886, 

 9:360.) 



Uranus. — Observations of the planet made by Dr. H. C. Wilson at 

 the Cincinnati Observatory in 1883 (recently published in Astron. 

 Nachr., 2730), seem to confirm Professor Young's observations (As- 

 tron. Nachr., 2545), that the equator of the planet does not coincide 

 with the plane of the satellites' orbits. 



Neptune: Satellite of Neptune. — Marth calls attention (Month. Not., 

 46: 507) to what appears to be a remarkable change in the position of 

 the plane of the orbit of Neptune's satellite. He noticed that the orbit 

 from the Malta observations of 1863-'64 did not agree with that from 

 the observations of 1852. The node and inclination obtained by New- 

 comb in 1874 showed a movement in the same direction, and tlie motion 

 of these elements is still further confirmed by the orbit recently pub- 

 lished by Professor Hall from his own observations at Washington. 

 The probable errors are so small that it seems hardly plausible or pos- 

 sible to attribute the change to systematic errors of observations. Mr. 

 Marth calls for careful observations to strengthen the evidence. 



REPORTS OF OBSERVATORIES. 



The following account of the recent activity of astronomical observa- 

 tories is compiled from all available sources, the " Vierteljahrsschrift" 

 furnishing, as usual, the data for most of the observatories, although the 

 latest reports there published are for the year 1885. I am indebted to 

 the directors of many observatories for the direct communication of 

 Information in regard to the institutions under their control. 



An alphabetical list of astronomical observatories, compiled by Mr. 

 Boehmer, will be found in the Smithsonian Report for 1885. 



M. Lancaster, of the Bruxelles Observatory, has published a useful 

 directory of observatories and astronomers. 



Algiers Observatory (1880). — The French Government has granted the 

 funds necessary for, the completion of the observatory, and two assist- 

 ants have been sent to join M. Trepied. A time service has been organ- 

 ized for the cities of Algiers and Tunis, and the observatory will co- 

 operate in geodetic work with field parties. Stellar photography will 

 receive special attention. The observatory possesses a spectroscope by 

 Thollon giving a spectrum 10 meters in length. 



Allegheny Observatory (1886).— The work during 1886 has consisted of 

 an extension of former researches on invisible radiations, and on the 

 absorption and radiation of .heat by the earth's atmosphere, and also of 

 researches upon the absolute temperature of the lunar surface. In con- 



