202 ASTRONOMY. | 



probable tliat C moves round a star wbicli belongs to tbis system, bu* 

 wbicb is not one of tbe tbree known, A, B, C. 



During- tbe first part of 1881, Mr. S. W. Burnbam was resident at tbe 

 Wasbburn Observatory at Madison, by tbe invitation of Governor Wasb- 

 burn. During tbe period April 23 to September 30, 1881, be discovered 88 

 new double stars, several of great difficulty, and measured no less tbau 

 1G2 double stars (eacb on tbree nigbts) selected from bis MS. Catalogue 

 of Double Stars. In tbe zone observations at tbis observatory during 

 tbe same period, 60 more double stars were found. Mr. Jedrzejewicz, 

 of Plonsk, bas publisbed during tbe year a continuation of bis double 

 star measures, wbicb appear to be remarkably consistent among tbem- 

 selves. He bas measured a great many of tbe neglected pairs of 

 Struve, eacb star on tbree or more nigbts. 



Tbe observations are given in tbe Astronomisclie Nachrichten, Nos. 

 2324-2107. 



Companion of Sirius : — An orbit of tbe companion of Sirins, based on 

 measures, bas been computed by Professor Colbert, of Cbicago. 



Tbe elements give tbe period as 49.G years. Tbe position for 1881.2 

 is p=45o.6, s = 9".9; for 1882.2, p = 43o.l, s=9".5. For 1890.2 tbe 

 position is p = 322^.2, s = 2".2, and at tbat date Sirius will be about 

 tbe most difficult known double. Tbis is about tbe minimum, accord- 

 ing to Professor Colbert. 



THE SOLAR SYSTEM. 



By far tbe most important papers wbicb bave appeared during tbe 

 year are tbose of Mr. George Darwin on tidal friction in connection 

 witb tbe bistory of tbe solar system.* Tbis paper forms one of a series 

 on tbe subject of tidal friction, wbicb bas been read from time to time 

 before tbe Koyal Society. An abstract of one of tbese was given in tbis 

 report for 1880. Tbe first part of tbis paper contains tbe investigation 

 of tbe cbanges produced by tidal friction in tbe system formed by a 

 planet witb any number of satellites revolving about it in circular orbits. 

 As tbe results cannot be conveniently stated witbout tbe aid of matbe- 

 matical notation, tbey are bere passed over. 



The previous papers treated of tbe efiects wbicb tidal friction must 

 bave bad on tbe motions of the eartb and moon, on tbe supposition tbat 

 time enough has elapsed for this cause to have its full effect. It then 

 appeared that we are thus able to co-ordinate together tbe various ele- 

 ments of the motions of these two bodies in a manner too remarkable 

 to be tbe product of chance. 



The second part of tbe paper contains a discussion of tbe part which 

 the same agency may have played in the evolution of the solar system 

 as a whole and of its several parts. 



*Ati accouut of a paper entitled "On the tidal friction of a planet attended by sev- 

 eral satellites, and on the evolntion of the solar system, by G. H. Darwin, F. R. S., 

 read before the Royal Society on January 20, 1881." 



