1871.] The Fuel of the Sun. 449 



in thickness. Even the pallid carbonic acid flame which 

 accompanies the pouring of the spiegeleisen has marvellous 

 illuminating power. 



The reader will now be able to understand my explanation 

 of the sun-spots, of their nucleus, umbra, and penumbra. 

 From what I have stated respecting the planetary dis- 

 turbances of the solar rotation, the photosphere should 

 present all the appearances due to the movements of a fiery 

 ocean, raging and seething in the maddest conceivable fury 

 of perpetual tempest. If the surface of a river flowing 

 peacefully between its banks is perforated with conical eddies 

 whenever it meets with a projecting rock or obstacle, or 

 other agency which disturbs the regularity of its course, 

 what must be the magnitude of the eddies in this ocean of 

 flame and heated gases, when stirred to the lowest depths 

 of its vast profundity by the irregular reeling of the solar 

 nucleus within. Obviously, nothing less than the sun- 

 spots; those mighty maelstroms into which a world might 

 be dropped like a pea into an egg-cup. 



When the photosphere or shell of combining gases is 

 thus ripped open, the telescopic observer looks down the 

 vortex, which, if deep enough, reveals to him the inner 

 region of dissociated gases and vapours. But these have 

 the opposite property to that which I have shown to belong 

 to flame ; they are opaque to their own special radia- 

 tions, while the flame is transparent to the light of the 

 inner portions of itself. Thus, the dissociated interior of 

 the solar envelope, though absolutely white-hot, will be 

 comparatively dark (direct experiment has proved that the 

 darkness of the spots is only relative). 



The sides of the vortex funnel will consist of a mixture 

 of dissociated gases, flaming gases, and combined gases, 

 and will thus present various thicknesses of flame, and 

 thereby effect the various shades of the penumbra. Space 

 will not permit me here to follow up the details of this 

 subject, as I have done in the original work, where it is 

 shown that if the telescope had not yet been invented, all 

 the telescopic details of spot phenomena might have been 

 described a priori as necessary consequences of the constitu- 

 tion I have above ascribed to the sun. 



Not merely the great spot phenomena, but all the minor 

 irregularities of the photosphere follow with similarly demon- 

 strable necessity. Thus the many interfering solar tides 

 must throw up great waves, literally mountainous in their 

 magnitude, the summits and ridges of which, being raised 

 into a higher region of the absorbing vaporous atmosphere 



