50 Mr. W. Pringle on the continuance of a Solar Spot. 



notice, had not I feared intruding on space, as I may even 

 now. 



The second view I had of the spot of this month was on the 

 13th, when it was within little more than four days of its dis- 

 appearance. Its general aspect was still in favour of its iden- 

 tity with the preceding. 



From what has been observed, I am inclined to conclude 

 that the solar spots may last much longer than we are yet 

 aware of; and that the want of sufficient observation alone 

 has restricted our knowledge of the true extent of their dura- 

 tion. No doubt it would occupy almost the entire time and 

 undivided attention of any individual to follow out their phases 

 and developments so as to satisfy the objects required : but 

 an association, I am informed, has recently been instituted for 

 the express purpose of observing and studying the spots in a 

 more systematic manner than has hitherto been attempted, 

 and to whose united labours, therefore, if published, we may 

 look for a mass of new matter and interesting information on 

 the subject, such as could not be expected from mere individual 

 and isolated observation. 



The spots seem almost the only inlets whereby to penetrate, 

 if possible, into the sun's physical character, with the excep- 

 tion of the phaenomena connected with eclipses ; and however 

 volatile and changeable they may appear, there is no good 

 reason to despair of yet reducing their evolutions to a system, 

 and even thus detecting laws which may bear upon the solu- 

 tion of the general physical organization of the sun. 



Submitting these somewhat desultory notices to your con- 

 sideration, 



I remain. Gentlemen, 



Your most obedient Servant, 

 Edinburgh, Dec. 15, 1848. W. Pr INGLE. 



P.S. Permit me to take this opportunity to state, what it 

 may perhaps interest Mr. Glaisher or others to know, that the 

 same distorted image of Mercury on entering the sun's disc 

 which one out of eight telescopes presented at the Greenwich 

 Observatory, was also observable here. The planet appeared 

 to me to enter like a black wedge, with undulating edges like 

 a Malay Krees or dagger, an appearance which 1 ascribed at 

 the time to the tremors of intervening smoke and vapours. 

 This could scarcely have been the cause at Greenwich, as the 

 seven other telescopes showed the planet round and clear. Dr. 

 Dick, of Broughty Ferry near Dundee, also described the ap- 

 pearance as an " indentation " on the sun's limb. — W. P. 



