1 62 Mr. GooDRicKE*s Obfervatiotis 



becaufe in that point the ftar has been obferved of about the 

 fourth magnitude at intervals much fliorter than in the third 

 point, lb that, if it had continued to diminiih, its diminution 

 would have proceeded at a more rapid rate, which ftill {hews 

 that there is at leaft a difference between thefe two points. 



With regard to the period of the variation, it is evident 

 from a collation of the preceding obfervations in a coarfe way,- 

 that it is nearly twelve days and three quarters. To determine it 

 with greater accuracy is a fubje<5l of confiderable difficulty, in 

 the prefent cafe ; for unlefs we can obtain very exacfl points of 

 comparlfon, the period would come out erroneous, efpecially 

 if deduced from intervals coniifting of only a very few periods, 

 as is the cafe here. However, as I have been able to obtain a 

 few obfervations of the middle of its obfcuration in the third 

 point accurate enough for our purpofe, I have formed the fol- 

 lowing calculation. 



Times of the middle of its obfcuration 

 in the third point. 



1784, Ocl. 6 

 — 18 



oa. 18 



— 3^ 

 oa. 6 



Hence the period on a mean is 1 2 1 9 r±= 

 In afcertaining the above times, I attended particularly to 

 the neareft obfervations both preceding and following. In the 

 manner above ftated the period may alfo lie deduced from the 

 middle of its obfcuration in the feventh point; but as thefe 

 obfervations are not fo exadt as the above, I fhall only, as a 



further 



