274>. VARIABLE STAINS, 



ing explanations, fuggefting prcvioufly a few plaufible con- 

 jectures, and fome inferences arifing from the obfcrvations 

 themfelves *. 

 Affumcd pofi- 1 ft. 'J'hat the body of the ftars arc dark and folid. 



^^'^r'u /I 2^1. Their real rotations on their axes are regular . 



I. I ha ftars .are o 



opakc. i. They Sd. That the furrounding medium is by times generating 

 have regular ro- ^,^j abforbin°^ its luminous particles in a manner nearly fimilar 

 tations. 3. Tjicir " 1 /• . • ^ -i, n t t , 



luminous ap- to ^^hat has been lately lo ingenioufly lilultrated by the great 



pcaiance is inveftigator of the heavens, E>r. Herfchel, with regard to the 

 caufed by an at- . , 7 ^ , ' ' ' ^ 



inofphcre like Um's atmofphere. 



that of the fun. 4iJi. Tliat thefe luminous particles are hut Jparingly difperfed 



vlns^zreCpT°^ '" *^^ atmofj)here furrounding the variable ftar of Sobiefki, 



xingly difperfed appears from the ftar being occafionally diminiflied to the 6.7 



trelted^f'-^"^ magnitude, and much lefs. July 4, 1799, it was of the 7th ; 



Sepiember 15, 1798, and Auguft 9, 1803, of t he 9th, if not 



invifihk. (See Table VII f.) Does not this indicate a very 



fniall portion of light on its darkened hemifjihere ? 



5. Probably oth. And may we not with much plaufibility confider therr^ 

 fmall patches : as fpots, fomewhat circular, or of no great extent ? for even 



on its brighteji hemijphere the duration of its full luftre is, on a 

 mean, only 9| days of the 62, or about one-iixth and f of its 

 circumference. (See Table VIJI. page 140.) The dimen- 

 fions therefore of the parts enlightened feem much circum- 

 fcribed, and can be tolerably eftimated, and confequently 

 may be reprefented very fmall, particularly if the poiveiful 

 effecl of a Ultle light and the length of time a briglit fpot is re- 

 maining in view be taken into confideration. 



6. Changeable 6th. And a further ground of prefumption that thofe prin- 

 in theirnature : ^|p^| bright parts are but flight patches is, that they undergo 



perpetual changes, and alfo that fuch changes are very vifible 

 lo us, for m oft probably they would be imperceptible, were 

 not the bright parts conlrafted by confiderable intervals or 

 diminutions of light. 

 ^. Anddcducible 7th, and laft. We may obtain fome idea of the relative 

 from the ?^^^0' fituaiion or intervals between thefe brigiit parts, by the obferva- 



* The reft of the paper is given without abridgement, and the 

 author himfelf fpeaks in the firft perfon. 



f The author refers to his tables in the Tranfa6lIons, of which 

 the abridged reftdt has been here given. 



tions 





