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IV. On the Continuance of a Solar Spot. 

 By W. Pringle, Esq. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



IN the notice last communicated respecting the duration of 

 a solar spot from August to November (Phil. Mag. Dec. 

 1848), I stated that I should not perhaps have it in my power 

 to observe its re-appearance in December, should it then re- 

 turn. I have had, however, the opportunity of making two 

 observations; one on the 8th, and the other on the 13th of 

 December. 



On the 8th there was a succession of spots, or clusters, follow- 

 ing each other at intervals in a straight line, and cutting down 

 in an oblique direction, as usual at this period. They were all 

 in thenorthern hemisphere,except one dispersed group of small 

 spots which appeared in the south-western portion of the sun. 



The first spot or group next the eastern verge, which con- 

 sisted of two rather large spots with some minor ones attached, 

 appeared too little advanced to have come on upon the 4th or 

 Sth — the time that the spot of November might be expected 

 — being only about two digits from the circumference. The 

 second spot, which was about three digits and a lialf advanced, 

 seemed to me to correspond to the place the November spot 

 ought to have occupied ; and upon examining it attentively, it 

 presented such features as might result from the further decay 

 of the spot since it was last seen and sketched by the writer 

 on the 19th of November. At that time it was nearly of a tri- 

 angular form, the longest side measuring about 45,000 miles ; 

 the interior space exhibiting a mottled ground, or shallow 

 speckled with small dark spots. It was then large enough to 

 be very plainly perceptible to the naked eye, as it had been 

 at each period of its appearance. 



If I have rightly recognised it in the spot of the Sth of De- 

 cember, it has dwindled into a comparatively small and un- 

 noticeable cluster, of an irregular outline, still preserving the 

 mottled penumbral interior studded with minute nuclei; and 

 this was one of the distinguishing characteristics of its past 

 appearance, that it uniformly presented a dusky ground inlaid 

 with lateral nuclei, never once resolving itself into anything 

 like a great central nucleus. 



The nucleus of September 21 st, which Mr. Weld estimated 

 at 1' 7""2 in its longest diameter (Phil. Mag. Dec. 1848. 

 p. 480), lay imbedded in the western portion of the spot, and 

 might be considered as the nucleal remains of one of the two 

 separate spots of August, and which I conceive had been con- 



