Sun Viewing and Drawing. 



441 



which commonly attend the life-history of a group of solar 

 spots — observing, in passing, that usually they burst out more 

 rapidly than they subside. Their formation commences gene- 

 rally with the appearance in the photosphere of one or more 

 small specks, of only a few seconds in diameter, which some- 

 times are penumbral (grey) in their tint, and sometimes 

 umbral, or blackish ; implying consequently a greater or less 

 amount of profundity — the deeper the blacker. 



This stage is not shown in the Plate, because, in fact, the 

 group had passed through it previously to its appearance upon 

 the disc, which revolves, be it remembered, upon an axis, in 



ER SO 



t?ni 



about twenty-five days. Fig. 1 was drawn when the leading spot 

 of the group had advanced about 3-£ minutes from the sun's 

 limb or margin, and which would therefore be on the third day 

 after its first entrance upon the visible disc. At this time 

 several bright streaks of faculae lay to the left of the group, 

 which from some cause or other is usually the side they are 

 wont to affect ; though this rule is by no means invariable, for 

 the facula3 frequently lie closely round the outer edge of a spot, 

 and sometimes they may be seen scattered to the right as well 

 as the left of a group. 



