492 Scientific Proceedings, Royal Dublin Society, 



The existence of powerful southerly currents was inferred from 

 the manner in which the umbrae of both — but specially of the preced- 

 ing spot — was invaded by bridges of photosphere, entering from the 

 southern side, and which promised rapidly to disintegrate the 

 entire spot. It is important to ascertain whether either of these 

 spots occupied the position of the original. The longitude of the 

 original was fortunately observed on the 9th, previous to the dis- 

 ruption. 



Again, on the 11th, after disruption, the longitude of the largest 

 of the two separated spots was taken; again on the 13th, and again 

 on the 15th. The daily amount of rotation during the first inter- 

 val, between the 9th and 11th, was 12°'5 ; that during the 

 second interval, between the 11th and 13th, 12'^*80 ; that during 

 the third interval, between the 13th and 15th, 12°-81 ; while the 

 average movement due to latitude 15°, according to Carrington, 

 is 13°-1. 



The differences, between the quantities are less than the 

 possible errors of observation, and therefore we seem justified in 

 assuming that the position of the spot observed was the same as 

 that of the original spot, and that the separation of the spots was 

 wholly due to the motion of the smaller, or the preceding, of the 



two. 



It is to be remarked that the difference of longitude of the two 

 spots had increased from 7° on the 11th, to 12° on the 15th ; and 

 as the primary spot appears to have retained its original longitude 

 unaltered, the secondary spot must have been endued with a proper 

 motion in longitude of its own, the motion being in that direc- 

 tion which would shorten the rotation period, and so approximate 

 to the rotation period of the equator. 



I would ask have we here any analogy to the state of affairs 

 disclosed by the Jovian atmosphere, in which the red and the 

 white spots, having nearly the same latitude, give different periods 

 of rotation, and are therefore endowed with a proper motion of 

 their own, as though different spherical envelopes of the atmosphere 

 were rotating in different periods ? 



Position of original spot, lat. 15 S., and it crossed the central 

 meridian, June 12, 7-75, Q. M. T. 



