318 ANNUAL OF SCIENTIFIC DISCOVERY. 



ent general displacement, which would be referred to the proper mo- 

 tion of the large star. Should, however, any mutual change of posi- 

 tion be detected among the comites, a wide field would be opened for 

 research among the fortunate possessors of competent telescopes. The 

 question of native or reflected light would, of course, be a difficult one 

 to deal with, its solution would, in fact, be impossible in the case of 

 orbits highly inclined to our line of vision ; but if bodies exist whose 

 revolutions carry them from side to side, or nearly so, with respect to 

 the central luminary, any periodical variation of light connected with 

 their positions in their orbits would, as indicating the existence of pha- 

 ses resulting from reflection, give sufficient evidence of their plane- 

 tary nature. 



Since the announcement of M. Goldschmidt, referred to above, M. 

 Secchi, of Rome, states that he has succeeded in seeing the satellite of 

 Sirius, with several contiguous luminous points; but in reference to 

 these- last, he asks, " Are they realities or illusions ? ' One he no- 

 ticed at 5". distance, and about 180 angle of position. He says he 

 mentions these observations to show the goodness of the telescope ; but 

 M. Goldschmidt's observations show that a much smaller instrument 

 will suffice when the air is favorable. 



On the Observed Motions of the Companion of Sirius. Mr. T. H. 

 Safford, of the Cambridge Observatory, has recently published the re- 

 sults of an inquiry into the observed motions of the companion of Sirius, 

 with a view of ascertaining whether it is in reality the disturbing body 

 which theory requires should exist. " That the companion of Sirius," 

 says Mr. Safford, " may produce the disturbances recognized, the faint 

 object barely visible in the largest class of telescopes must have a mass 

 nearly two-thirds that of Sirius itself. It is difficult to believe this ; 

 but as the evidence of this year (1863) shows, we may be compelled 

 to do so." 



" There are three hypotheses logically possible with respect to the 

 new star. It may be either unconnected with the system of Sirius, or, 

 secondly, a satellite, but not the disturbing body, or, thirdly, the dis- 

 turbing body itself." Opposed to the first hypothesis is the improba- 

 ble supposition, " that the small star can partake in the great proper 

 motion of Sirius without being physically connected with it ; " and if we 

 adopt the second hypothesis, the disturbing body, judging from the 

 feeble light of the companion recognized, must have less light, or be 

 absolutely invisible. " It ?>, therefore" concludes Mr. Safford, " highly 

 probable that the disturbing body has been actually found ; and that what 

 was predicted by theory has been confirmed by sight. The importance 

 of continued observations on Sirius cannot be too highly felt. The 

 companion must be measured the coming year, and for several years ; 

 while Sirius itself should be reobserved with meridian instruments." 



VARIABILITY OF NEBULAE. 



In the Annual of Scientific Discovery, 1863, pp. 317-18, an account 

 was given of the discovery of the disappearance of a nebula in the con- 

 stellation Taurus, toward the close of October, 1861. During the past 

 year the announcement is made that the nebula in question has reap- 

 peared, without change of place, but materially fainter than when first 

 observed. In addition to this interesting statement, another still more 

 remarkable has also been recently brought out. 



