450 On the Origin of the Light of the Sun and Stars. 



time, but it is only lately that they have become the subject of 

 scientific study. The following sketch from solar photographs 

 taken at theKew Observatory will give an idea of these curious 

 objects :— 



Left Limb of the Sun, 

 1363, July 5th, 12h. 24m. p.m. 



Left Limb of the Sun, 

 1863, July 6th, llh. 40m. a.m. 



Left Limb of the Sun, 

 1853, July 10th, 12h. 17m. p.m. 



In the first of these pictures we perceive a group consistin g 

 of two spots, which has just been brought into the field of view 

 by the rotation of our luminary. It will be noticed that, beyond 

 the spot at the extreme edge, there is a slight luminous thread, 

 otherwise this spot would have produced an apparent indentation 

 in the sun's limb. In the next picture the group has advanced 

 a little further into the disc ; and we now see a large quantity 

 of bright flocculent matter floating about chiefly between the 

 two spots. We likewise perceive from this, as well as from the 

 previous picture, that the circumference of the disc is less lumi- 

 nous than its more central portions. The second picture 

 affords us also an opportunity of observing minutely the two 

 spots which form the group. We see that each consists of a 

 black nucleus, accompanied by a penumbra, which, in the left- 

 li.'ind spot, is almost, if not quite, to the left of the nucleus. In 

 1 he t liird picture, that group has advanced nearly to the centre 

 of the disc ; and here we find, in both spots, that the nucleus is 

 very nearly central with respect to the penumbra, and that 

 there in a total absence of bright flocculent matter, or faculae, 

 as this is sometimes termed. 



By the nearly unanimous opinion of observers, spots have 

 been regarded as breaks in I ho photosphcro of the sun, through 

 which his comparatively dark body becomes visible. The first 

 scientific observer was Dr. Alexander Wilson, of Glasgow, who 

 upheld this hypothesis by endeavouring to show that when a 

 spot is near the sun's limb, the nucleus is generally nearer the 



