POSITION OP DOUBLE STAllSr f219 



tsedlng, and the obferved diftance, near 2 diameters of the large Obfervatiom 

 flar, required it. With a proper velocity, let it be in motion refpedUngllMt* 

 towards the place where it may now be feen at the fame d if- changes of re- 

 tance from Caftor, but under an angle of pofition only 10^ 53' |n ft^rf «trem«- 

 north preceding. It may then be admitted, that a fmall decreafe ly near each 

 of the diftance which would happen at the time when the angle °*^'* 

 of pofition was 21^ 50', could not, have been pej;ceived; fo that 

 the gradual change in the obferved angle of pofition, as well as 

 the equality of the diflance of the two flars, will be fufhciently 

 accounted for. But the admiffion of this hypothefis requires, 

 that a Geminorum and the folar fyflem fhould be at refl; and, 

 by the obfervations of aflronomers, which I fhall foon have 

 occafion to mention, neither of thefe conditions can be con- 

 ceded. 



{b) If, according to No. 2, we admit the motion of a, wq 

 fliall certainly be more confifient with the obfervations which 

 iflronomers have made on the proper motion of this fiar * ; and, . » 



&s a motion of the folar fyfiem, which I fhall have occafion to 

 mention hereafter, has not been rigidly proved, it may, for tha 

 fake of argument, be fet alide ; nor has a proper motion of the 

 ilar X been any where afcertained. The retrograde annual 

 proper motion of Cafior, in right afcenfion, according to Dr. 

 Mafkelyne, is 0'',103. This, in about 23| years, during which 

 time I have taken notice of the angle of pofition and diftance 

 of the fmall fiar, will amount to a change of nearly 2'',47, ' 

 Then, if we enter the fhort Table I have given in No. 2, with 

 the motion aP, we find, that in the firfl quadrant, where the 

 fmall flar is placed, the diftance between the two flars will be 

 diminillied, and the angle of pofition increafed. But fince it 

 appears, by my obfervations, that the difiance of the frars is 

 not lefs now than it was in 1780; and that, infiead of an in- 

 creafe in the angle of pofition, it has actually undergone a 

 diminution of nearly 22 degrees; it follows, that the motion n 

 of a Geminorum in right afcenfion, will not explain the 

 obferved alterations in the fituation of this double flar, li^ 



* See Tobije Mayeri Opera inedita. De motu jixarum propria, 

 page 80. Alfo Dr. Maskelyne's firfl Volume of Obfervations. Ex- 

 planation and \5iQ of the Tables, p. iv. Or Mr. Wollafton's Ai- 

 tronomical Catalogue, end of the Preface. Likewife Connoiffance des 

 ^empspQur l" Annie VI. p. 203. Sur le Mowvement particulier pro* 

 pre a differentes Etoilesj par Mons, De la Lande, 



according. 



