442 Sun Viewing and Drawing. 



At this stage of the formation of the group (Fig. 1) it may 

 be observed how the umbra or darker parts lie on the inner 

 side of the penumbras or lighter parts — a circumstance this 

 which is highly characteristic of a group of spots, especially 

 the more subordinate outlying ones, and also in its earlier 

 stages, however it is to be accounted for, though it would seem 

 to result from forces acting either from the centre, towards the 

 circumference of the disturbed area, or vice versa. At this 

 time the total portion of the photosphere displaced by the 

 various spots composing this group amounted to upwards of 

 400,000,000 square miles — an enormous area, indeed, as com- 

 pared with aught terrestrial, but still far less extensive than is 

 often the case on the surface of the mighty sun. Indeed, 

 within twenty-one hours after Fig. 1 was drawn, the displace- 

 ment of photosphere had reached about 778,000,000 square miles 

 (see Fig. 2), and the group even then was not fully developed, 

 which occurrence took place on Jan. 26, and when the whole 

 area of this group (and there were others on the sun at the 

 time) amounted to the enormous sum of 1,545,000,000 square 

 miles, or about eight times the superficies of the terraqueous 

 globe ! The writer has, however, observed them even larger 

 than this. But to return to our group as it appears in Fig. 2. 

 The umbra of the principal spot (which is almost invariably 

 the preceding one in the order of their advance across the 

 disc) was now well surrounded by penumbra on all sides, and 

 it moreover consisted of matter of two distinct tints — each, 

 however, much darker than the penumbra — and the lighter of 

 which two constituted the umbra, and the darkest and deepest 

 the nuclei, of which there were two or three. The way in 

 which the penumbra is usually marked with streaks, radiating, 

 as it were, from the umbra, is now very apparent ; indicating a 

 current of some sort setting in, either the circumference to the 

 centre, or from the centre to the circumference, and perhaps 

 also either a down-rush or an iip-rush of gaseous matter. 

 That it was a down-rush on the present occasion seems 

 strongly indicated by a phenomenon to which attention is 

 directed by the writer in vol. xxvii., p. 185, of the Monthly 

 Notices of the Royal Astronomical Society. He began to 

 make a drawing of this spot at 11 a.m., Jan. 25, and observed 

 at that time a small patch, of an almost umbral tint, at the 

 upper edge of the penumbra (this patch may be seen in 

 Fig. 2). He drew it, as it then appeared, exactly on the 

 margin. But by the time he had finished the spot, as well as 

 others on the disc, upon looking over his work, he found that 

 the small patch was no longer at the margin. Believing he 

 must have blundered, he altered it ; but in an hour or so 

 afterwards he observed that it was conspicuously removed from 



