Mr. W. Pringle on the Duration of a Solar Spot. 461 



after the 17th. On the 27th it was about half a digit from the 

 sun's western margin, and probably disappeared the day after ; 

 but cloudy weather prevented it being followed. 



About a fortnight afterwards, on the 13th of October, I 

 descried a long lenticular-shaped spot about a quarter of a 

 digit advanced on the sun's eastern limb. This I had little 

 doubt was the spot on its return ; and, as it came on, the ge- 

 neral resemblance confirmed its identity. It was, however, 

 much contracted in dimensions, measuring about 44,000 miles 

 when near the sun's centre. The irregular pointed outline 

 was still prominent, though the projections were less than on 

 its previous appearance. 



On the 26th of October I saw it as a very dim dot or line, 

 scarcely distinguishable from the line of circumference of the 

 sun's western limb. 



On the 9th of November, at some distance north of the point 

 of Mercury's entering the disc, a faint depression, having the 

 appearance of a spot of some size, was visible. This being the 

 very time when the spot of October might be expected to re- 

 turn, I felt confident it was the same ; and its further progress 

 confirmed the identity. It was again contracted much in size, 

 being somewhat triangular in shape. 



If the inferences above stated be well-founded, the spot will 

 have lasted about ninety-five days. Whether it will yet make 

 another revolution, or half a one, remains to be seen; but I 

 shall not probably have it in my power to make observations 

 at the period of its next appearance. It may be looked for 

 on the 4th or 5th of December. 



In many respects this spot was a remarkable one, and in all 

 likelihood did not escape the observation of the illustrious 

 author of the Cape Observations, whose chapter on solar spots 

 is so interesting. 



I should be happy if you think this worth noticing in your 

 Journal as a report of some particulars to which my attention 

 was directed, and which more profound observers may have 

 overlooked. 



The opinion of Dr. Dick, author of The Sidereal Heavens, 

 &c, to whom I submitted the observations of August, Sep- 

 tember and October, that in all probability the spots were 

 identical, according to the grounds stated, has the more em- 

 boldened me to address you. 



I am, Gentlemen, 



Your very obedient Servant, 



Edinburgh, Nov. 81, 1848. W. Pringle. 



