408 THE CHEMISTRY OF THE SUN. [CHAP. 



smoke or steam. We mention also, in passing, another thing 

 which has been shown by our large instrument at Princeton that 

 the apparently bulbous, finger-tip-like terminations of the penumbral 

 filaments are often, under the best circumstances of vision, resolved 

 into fine, bright, sharp pointed hooks which look like the tips of 

 curling flames." 1 



Professor Hastings seems to have found his smoke view of 

 sun-spots strengthened by the appearance of the edge of the 

 penumbra. To the eye the outer edge, where the half tone is 

 in contrast with the photosphere, seems darker than the one 

 which is in contrast with the black nucleus. This is a sub- 

 jective appearance merely ; as shown in photographs, the inner 

 edge is not brightened. 



3. By the hypothesis such falls of cooled material must take place 

 in different degrees and in greater or less quantity on all parts 

 of the- solar surface. 



From this it follows that there should be observed on the 

 sun very definite phenomena of the same kind but very differ- 

 ent in degree ; and that if some of the phenomena are limited 

 to certain regions, as we shall afterwards find them to be, others 

 are universally distributed over the sun's surface. As a matter 

 of fact such definite phenomena differing only in degree are 

 well known. I refer to each in turn, beginning with the most 

 general. 



(1) Pores. When we look at the sun what one sees is first a 

 bright disc, which is slightly dimmed at the edge ; on examining 

 the disc carefully, what we further see is a strange mottling of the 

 whole surface. The mottling is very often very delicate ; but 

 everywhere, in all parts of the sun, near the poles, near the solar 

 equator, and universally, we get this strange mottling. Fine dots 

 called granulations or pores are everywhere visible, and each pore 



1 Young, Nature, Nov. 17, 1886. 



