4Q2 PHILOSOPHICAL TRANSACTIONS. [aNNO 1774. 



other appearances, that are discernible on the surface of the sun, besides the 

 spots properly so called; viz. the faculae, luculi, &c. as described by Scheiner 

 and Hevelius. But all these phenomena seem to be so different from any thing 

 above considered, and so unconnected with the present discovery, that little 

 assistance can be brought from that quarter towards a right conception of them. 

 As to the faculae, or brighter parts of the sun, we are at a loss for their origin. 

 It may in general be remarked, that though we have obtained an experimental 

 proof, that the luminous matter acquires some degree of shade, when forming 

 the sides of an excavation, yet it is uncertain if this be merely the effect of 

 position, and much more so, if any different modification of position could ever 

 dispose it to put on a brighter or more fulgid appearance. Yet, after all, may 

 not these faculae, &c. depend on some irregularities in the bright surface of the 

 sun? For may not the luminous matter, by being agitated by the same cause 

 to which the spots owe their origin, though in a less degree, have its surface 

 perpetually disturbed, and made irregular, and thus give occasion to a variety of 

 light and shade, sufficient perhaps to produce the phenomena under consi- 

 deration.' And does not this conjecture receive further confirmation, when we 

 consider, that these faculae, &c. are found only in that zodiac, within which the 

 spots appear, and that they always abound most in the neighbourhood of the 

 spots themselves, or where spots recently have been? For in those undisturbed 

 regions of the sun that lie towards his poles, and where no spots ever appear, 

 and which Scheiner calls the plagae aequabiles, we never discover any diversity of 

 appearance. 



Thus Dr. W. has endeavoured to give a general idea of the production, 

 changes, and decay of the solar spots, considered as excavations in the body of 

 the sun; a thing which seems to be established from the observations described 

 in the first part of this paper. But concerning the nature of that mighty 

 agency, which occasions those amazing commotions in the luminous matter, 

 or concerning the density, viscidity, and other qualities of this matter, or the 

 manner in which it is disturbed in the middle zone only, and not at the polar 

 regions, and many such other questions, he freely confesses, that they far sur- 

 pass his knowledge. 



]J. Astronomical Observations by the Missionaries at Pekin. Transmitted to the 

 Supra- cargoes at Canton, by the Rev. Father Louis Cipolla, of the Tribunal 

 of Mathematics, and communicated to the R. S. by the Court of Directors of 

 the East India Company, p. 31. 



Preface by the Astronomer Royal. — Most of the following observations appear 

 to have been made with a telescope of 8 feet, to which a micrometer, for mea- 

 suring differences of right ascension and declination, was occasionally adapted. 



