VARIAfeLE STARS. ^'() 



^d!y, The interval of 46 days between the two minima of ^*P[:^"ation by 

 July 19 and Sept. 3 ; See Table X. the pScal 



3dly, The long decreafe of 38 days between July 27 and variauons and 



c 4 o 1 irregularilies of 



Sept. 3, and ^ ^ light in the ftar 



4thly, The rapid increafes of 3 and 14 days between the 19inSobiefkPs 

 and 27 Ih of July, and the 3d and 17th of September, ^^^^'^' 



As alfo the other intermediate changes, yet I mufl again 

 repeat, particularly as a few days error may occafionally pro- 

 ceed from the obfervations, that by thefe Iketches it is not 

 meant to give exa6l drawings of the fize, diflances or altera- 

 tions of the fpots, but merely to lliew how the changes may- 

 take place, as, I believe, nothing of the kind has hitherto been 

 offered to the public, either with or without corroboraUi.gob* 

 fervations ; nor do I prefume to think, that the explanations 

 are the only ones or beft can tliat be imagined, the more fo, 

 as they folely refer (for greater limplicily) to the fiar's 

 equator, while pofiibly, were the fpots placed in a northern or 

 fouthern latitude, or permanent ones near the poles, or were a 

 proper inclination, given to the polar axis, they might be more 

 fatisfa6lory : however, the materials themfelves, the obfcrva* 

 iions and dcduSlions will I flatter myfelf ever be acceptable, and 

 contribute to facilitate future conjectures, which froni an allow- 

 able analogy may extend to fimilar parts of the ftarry fyftera, 

 with regard to the probability of eftabl idling whether any of 

 the mofl irregular or particular changes may not return at Jixt 

 periods, or after a certain number of rotations. I think we can 

 entertain but flight hopes of it, owing to i\\Q great fiuduationoi 

 the luminous matter, as (hewn by the perpetual varying of the 

 apparent revolutions, magnitudes, &c. See Tab. IX. X. and VII, 

 Still it is natural to fuppofe, that fome parts of llic atmolphere 

 of this ftar may have a lefs tendency than others to become 

 luminous, fo as to promote at different times, fimilar appear- 

 ances ; and indeed that is flrongly indicated by the intervals of 

 the 7ninima being far moreregular than thofe of ihefull brightfiejs, 

 which, with other reafons induce us to (ufped even that one 

 of its hemifpheres is lefs favourably conftituted or qualified, 

 than the other for the generating of thefe particles, although 

 they do occafionally encroach on both fides, as appears by the 

 obfervations between June and Augull, See Phil. Trans, for 

 1797, or the eight Iketches of 179o, and likewife in 1797, fee 

 Tab. VII.' when during three months it was only reduced to the 



5 or 



