THE FUEL OF THE SUX. 83 



solar prominences will at once perceive how all these expecta- 

 tions are fulfilled by actual observations, especially by the more 

 recent observations of Zollner, Secchi, etc., which exhibit the 

 typical solar prominence as a stem or jet rushing upward 

 through some restraining medium, and then expanding into a 

 cloudlike or palm-tree form after escaping from this restraint. 

 I need scarcely add that the clashing tide waves are thefaculce, 

 and the vortices the sun-spots. 



My present business, however, is to show how these vortices 

 and eruptions this down-rush in one part of the solar atmos- 

 phere and up-rush in another contribute to the permanent 

 maintenance of the solar light and heat. It must be under- 

 stood that these outbursts are only visible to us as luminous 

 prominences during the period of their explosive outburst, 

 and while still subject to great expansive tension. Long after 

 they have ceased to be visible to us their expansion must con- 

 tinue, until they finally and fully mingle with the medium into 

 which they are flung, and attain a corresponding degree of 

 rarefaction. This must occur at tens and hundreds of thou- 

 sands of miles above the photosophere, according to the magni- 

 tude of the ejection. The spectroscopic researches of Frank- 

 land and Lockyer having shown that the atmospheric pressure 

 at about the outer surface of the photosphere does not far 

 exceed that of our atmosphere, I may safely regard all the 

 upper portion of these solar ejections as having left the solar 

 atmosphere proper, and become commingled with the general 

 interstellar medium. 



If the sun were stationary, or merely rotating, in the midst 

 of this universal atmosphere, the same material that is ejected 

 to-day would in the course of time return, and be whirled into 

 the great sun-spot eddies ; but such is not the case ; the sun 

 is driving through the ether with a velocity of about 450,000 

 miles per twenty-four hours. 



What must be the consequence of this motion ? The sun 

 will carry its o\vn special atmospheric matter with it ; but it 

 cannot thus carry the whole of the interstellar medium. There 

 must be a limit, graduated no doubt, but still a practical limit, 

 at which its own atmosphere will leave behind, or pass through, 

 the general atmospheric matter. There must be a heaping or 

 condensation of this matter, in the front, a rarefaction or wake 

 in the rear, and a continuous flow of newly encountered atmos- 

 phere around the boundaries in the opposite direction to that 

 of the sun's motion. The result of this must be that a great 



