1865.] Prof. Phillips Physical Aspect of the Sun. 49 



appear for the most part oblong, but with no systematic concurrence of 

 direction. The comparison used by another astronomer*, of an irre- 

 gularly heaped surface of rice, here collected into ridges, there sunk into 

 depressions which seem to be occasionally deepened into pits, has its advan- 

 tages. But upon the whole I prefer to be content with the less definite 

 analogy to an irregular granulated and pitted surface, composed of small 

 prominent lights complicated with intermediate shades of different in- 

 tensities. 



PART II. Details of Spots. 



In the midst of the general ground thus described, spots make their 

 appearance, grow, change, and decay under the observer's eyes. Seldom 

 indeed, as once to Mr. Carrington, does it happen that a spot appears 

 suddenly ; its growth, change, and decay are all usually slow too slow to 

 be positively noted and measured except at intervals of hours and days. 

 We notice occasionally spots of minute size which have no surrounding 

 penumbra ; these may be either very black or only dark. These often occur 

 in considerable numbers near a large spot well enclosed by penumbra, as in 

 spot No. 2, 29th March (Drawing No. 7). On the 30th of March one 

 of these had acquired a slight penumbra, several of the others had disap- 

 peared. The several small spots represented (Diagr. No. 6) amidst a mottled 

 surface of faculse and granulations had no penumbra ; one was dark, but 

 not black. Some of the spots here referred to appear to be less than 500 

 miles across, and many are less than 1000. They are occasionally in twins, 

 and not unfrequently disposed in groups which may eventuate in a spot, or 

 in a long sinuous tract having some relation of origin to greater spots near 

 them. The greater spots with large penumbral regions have usually very 

 irregular boundaries, and equally irregular black nuclei. In them it is 

 quite usual to perceive two, three, or more nuclei ; but in such cases the 

 term nucleus is but little fitted to describe these often narrow winding and 

 branching spots which appear within the irregular space. The boundaries 

 of that space are in a certain degree conformed to the black nuclei. Many 

 large spots of this kind undergo very considerable changes in the course of 

 one day. A complicated spot which measured about 20,000 miles across 

 on the 29th of March, lost its penumbra and was reduced to separate 

 nuclei on the 31st ; while a curved collection of small dots near it was 

 concentrated to a small group, and two other obscure dots expanded a 

 little and became three. In this state, with but slight further change, they 

 all passed across 60 of arc. 



In complete contrast with these examples is the spot No. 4 [in the 

 diagram of March 29], which with very little observable change in itself, 

 and with no additional productions near it, has been traced across the sun's 

 disk through a third of the circumference. I present drawings of this 

 spot as it appeared with powers of 75 and 1 35, for the purpose of marking 

 the unusual persistency of its characters, and describing its relations to the 



* Mr. Stone. 

 VOL. XIV. E 



