276 



KNOWLEDGE. 



[December, 1903. 



N or has this great outburst come alone ; two others, 

 both of very considerable size, have accompanied it. The 



Fig. 1.— The Sun, 1903, November 4d. 12h. 21m. 20s. 



first of these appeared at the east limb of the 

 sun on October 2, its heliographic latitude being 

 18° North. For sake of clearness of reference 

 I will call this the Northern Group. The second, 

 the one to which I have already alluded, began 

 to appear at the east limb on October 4, its lati- 

 tude being 21° South, and I will refer to it in 

 future as the Great Southern Group. The third, 

 and smallest of the three, was in many ways the 

 most interesting, inasmuch as its passage across 

 the central meridian of the sun was synchronous 

 with a magnetic storm of the very first order. I 

 will therefore refer to this group as the Storm 

 Group. 



The Northern Group, at its first appearance, 

 consisted essentially of a regular or normal spot, 

 followed by a number of very small companions 

 in a long stream. The area of the chief spot 

 was about 270 millions of square miles, but when 

 it had returned to the east limb on October 29 

 for its second apparition, it consisted chiefly of 

 two large regular spots, and the total area of the 

 two was fully 800 millions of square miles. It 

 began to pass the central meridian about 4 o'clock 

 on the morning of November 5, and had com- 

 pletely passed by 11 o'clock on the morning of 

 November 6. At this time the area of the group 

 amounted in the whole to 1100 milhons of square 

 miles ; the two principal spots having areas of 650 

 and 310 respectively. A distinct, but quite minor 

 oscillation of the magnets took place during the 

 evening and night of November 5, that is to say, 

 just when this group was in mid-transit. 

 Fig. 1 shows this Northern Group approaching the 

 central meridian. 



The Great Southern Group was of quite another order. 

 Like the Northern Group it formed in the unseen hemi- 

 sphere, but its formation was preluded by the ap- 

 pearance of a short-lived spot from September 10 

 till September IG. This spot, however, died out 

 before reaching the west limb, so the Great 

 Southern Group was a new formation. It, 

 therefore, was a young group when it was first 

 seen on the east limb on October 4 and .5, and 

 must have grown with extreme rapidity. At 

 first it was practically a single huge spot of 

 nearly 7° in greatest breadth, and about 15° in 

 greatest length. But it was speedily intersected 

 by an exceedingly lieautiful and complex system 

 of bright bridges which soon divided it up, and a 

 broad bright region formed about the centre of 

 the spot, making a wide gap between the pre- 

 ceding and following portions. Its total area on 

 October 9 exceeded 2400 millions of square 

 miles. The first member of the group reached 

 the central meridian about October 10, 19 hours ; 

 the last spots crossed about October 12, 2 hours, 

 civil time ; and the group passed out of view at 

 the west limb on October 17 and 18. Its second 

 appearance at the east limb occurred on Novem- 

 l)er 2, and on November 4, the day represented 

 in Fig. 1, it was seen as a very long stream of 

 spots, or rather as four distinct groups following 

 each other at short intervals. It passed off at 

 the west limb for the second time on November 

 14 and 15. 



Shortly after this group had completely passed 

 the central meridian (see Fig. 2), a very marked 

 magnetic disturbance commenced. The move- 

 ments of the needle began about October 12, 18 



Fia. 2.— The Sun, 1903, Oftober 12d. llh. 36m. 49s. 



hours, that is to say about 6 o'clock in the evening, and 

 from 8 o'clock in the evening until about three in 



