abstracts: astronom-* 205 



the motions of certain stars in the line of sight. Eowever, on accounl 

 of the strong colors existing in the flinl and crown glasses of the objective 



no better results could be obtained than those given by a very much 

 smaller instrument. It seemed proper, therefore, to discontinue spec- 

 troscopic investigations. 



As to the observations included in this volume there are then: The 

 satellites of Mars, measured with respect to the planet a1 five opposi- 

 tions. These moons were discovered at the Naval Observatory, and 

 their orbits were first determined there. They are interesl ing when any 

 questions are considered relating to the evolution of the solar system, 

 since they revolve about Mars in 7 h 39 m and 30 h 18 m , respectively, 

 while Mars itself rotates on its axis in 24 h 37 m . Also, there are some 

 very curious perturbations of the elements of these satellites, caused by 

 the flattening of Mars. 



The four bright moons of Jupiter were observed in pairs, according to 

 the method of Otto Struve, during four oppositions. But since the 

 bright moons can probably be measured more accurately in this way 

 with the heliometer than with the equatorial the work was discontinued. 

 Satellite VI, however, was observed with reference to fixed stars during 

 the opposition of 1905-06, and has been measured regularly in that way 

 since that time. 



The satellites of Saturn were observed in pairs, using at first fifteen 

 combinations, which number was afterwards reduced to nine. At one 

 opposition, 1895, Hyperion was referred to Saturn. 



The four moons of Uranus were referred directly to the planet, and 

 the combination Titania-Oberon was also made. The satellite of Nep- 

 tune was followed at every opposition except one. 



These satellite measures are a proper extension of the work accom- 

 plished at the old Observatory site, which included rather elaborate 

 monographs on the moons of Mars, Saturn, Uranus and Neptune, as 

 well as the discovery of the very curious motion of the line of apsides of 

 the orbit of Hyperion. The movement of the node and inclination of 

 the orbit of Neptune's satellite, probably arising from a flattening of the 

 planet, was pointed out by Mr. Marth as a result of the comparison of I he 

 Malta and Washington observations. 



For the measures of diameters during the years 1900, 1901, and 1902 

 color cells were used to absorb the outstanding blue light of the secon< lary 

 spectrum, these cells being placed in front of the eye-pie, 



A list was observed of 593 double stars. It was not intended to at- 

 tempt any thing in the way of finding new doubles, but only to furnish 

 needed measures of known pairs. 



