19. Sunspots and Prominences. 
By J. EVERSHED. 
[With Plates X VII—XIX.] 
disc baffle us still. We examine them, photograph them, and 
lopment follow certain laws; we now know something about 
we know about them, the more mysterious they become. 
have gained one step, however, in being able to say 
clouds floating in a sea of light . they are not, as Herschel 
believed, rifts in a burning atmosphere through which we see 
4 cool, solid, habitable globe below. Even the intensely black 
centre of a sunspot—as it appears to us—can only be spoken of 
48 cool or dark by contrast with the surrounding regions, for 
Passing out of sight on the western limb as the sun rotates and 
pea 
4 b : : i 
and did not die out until the end of April, 1909. The life 
histori : : there is a general 
es of these long-lived spots differ, but nig ‘ak black 
iat Wescent state and regular form, This also gradually dimin- 
In phot _ 1) one sees the radial 
Gib of the ay pews 8, proc surrounds the 
