Intelligence and Miscellaneous Articles. 311 



removed from above the penumbra ; leaving in general only the 

 elongated forms of the brightest self-luminous clouds of the photo- 

 sphere, which, converging towards the nucleus, are seen projected on 

 the penumbra, and extending often beyond its interior edge on to 

 the umbra, like bright straws, as I have previously described them. 



The rotatory motion of a profound spot may be produced by the 

 exploded gas having acquired a whirlwind sort of action, and thus 

 carrying round the parts of the different strata affected by it in the 

 same direction. But though I have observed this motion with cer- 

 tainty on two or three occasions, I believe it to be exceedingly rare 

 — at least in this class of spots. 



2. The superficial spots. — These appear, from the general tenour 

 of my observations, to be almost always produced by convulsions of 

 some kind in the photosphere itself, or at a small depth below it. 

 But, from the extraordinary variety of the effects, I confess that I 

 am not prepared to add anything to the suggestions already advanced 

 as to the character of those convulsions, or the means by which they 

 may be produced. Many of the spots which seem to be thus formed 

 are remarkable for the immense extent of the abrasions, so to speak, 

 of the photosphere, leaving large areas of the penumbral stratum ex- 

 posed, but with none, or scarcely any, of it removed so as to show 

 the cloudy stratum and thus to produce any umbra at all. In these 

 cases, the exposed penumbral stratum has rarely any bright lines of 

 the photosphere projected upon it. Another remarkable fact is, that 

 at some times, for months together, there is a tendency to the for- 

 mation of small superficial spots in considerable number (as from 8 >/ 

 to 12), arranged nearly in an elliptic form, the longer axis being 

 nearly parallel to the sun's equator. I have occasionally observed 

 more than one of these curious elliptic outbreaks in different parts 

 of the sun at the same time. And there is almost universally this 

 singular feature attending the spots thus arranged : the penumbra of 

 each is expanded outwards from the centre of the ellipse. Not unfre- 

 quently there is in such cases nothing but the penumbra exposed, no 

 umbra being visible : and even when a small umbra is exposed, the 

 interior edge of each spot is formed by the photosphere, no penum- 

 bra appearing on that side. The whole appearance gives the idea 

 of a prodigious and widely extended force emanating from the centre 

 of the ellipse at a level but little below the photosphere, and acting so 

 obliquely as to disturb that stratum only at great distances from the 

 centre. 



P.S. — I am indebted to the kindness of Mr. Birt for some extracts 

 from an elaborate paper by Sir William Herschel, with which I was 

 previously unacquainted. It forms a part of vol. xci. of the Philo- 

 sophical Transactions, and was read on the 16th of April 1801. The 

 observations of several years are referred to in it ; and some of them 

 are so remarkable, and so much to the point on the subject of the 

 telescopic appearance of the general surface of the sun, that I think 

 it will be highly desirable to quote a few passages most clearly 

 expressing the conclusions to which that admirable observer had 

 arrived. 



