66 Prof. Phillips on a Zone of Spots on the Sun, [Mar. 22, 



24th of February. Reappearing with similar splendid companion ridges 

 of mountainous clouds, but much reduced in size, and altered in every 

 part, it was observed again from the 12th to the 17th of March, after 

 which the weather allowed no further opportunity. Two sets of drawings 

 of this remarkable spot are presented to show its growth, development, 

 and decay (PI. II. figs. 7, 8, 9, and 10, 11, 12). The apparent path on 

 the sun's disk is given for each period of appearance — the two paths 

 differing by reason of the change in the apparent place of the sun's equator 

 (see Diagram No. 3). 



Diagram 'No. 3. 



But few examples occur of such large penumbral tracts grouped about 

 so many dark and half-darkened umbrse. On the sun they occupied, as 

 already stated, a tract about 12° in length, not quite parallel to the 

 equator ; and may be compared to some of those which are most conspi- 

 cuous in Mr. Carrington's plates. 



From what has been observed, it appears that, in a given zone of spots, 

 not only are the aspects of the particular spots much diversified, but 

 further, that the changes to which they are subject offer much variety. 

 These circumstances seem to point to particular local conditions as the 

 cause of the diversity of appearance, though it may be possible to refer to 

 other influences the frequency of their occurrence, if not the fact of their 

 occurring at all. 



The five spots now under review lie within an arc of longitude of 205°, 

 leaving 155° in which as yet no spot has lately been seen. In 1864, during 

 the months of March and April, a zone of spots, also five in number, and on 

 the same side of the equator, was contained within an arc of longitude of 

 243°, leaving 117° at that time free from spots. There was then within 

 the same arc of 243° a pair of spots in about the same latitude, but in the 

 opposite hemisphere. Taking these into account, the average of the arcs 

 of longitude between the spots was about 49°. In the case of the spots 

 lately passing it was 51°. Twenty-six revolutions would have brought the 

 middle of that zone of activity of 1864 to nearly the same place on the 

 sun's disk, as the group now imder consideration. 



To whatever cause we may ascribe the fact of the breaking out of these 



