THE FUEL OF THE SUN. 19 



of that which would be due to the original upheaving force, 

 is to be expected. 



The reader who is acquainted with the phenomena of the 

 solar prominences will at once perceive how all these expec- 

 tations 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 rush- 

 ing upwards through some restraining medium, and then 

 expanding intoa cloud-like or palm-tree form after escaping 

 from this restraint. I need scarcely add that the clashing 

 tide waves are the faculce, and the vortices the sun-spots. 



My present business, however, is to show how these vor- 

 tices and eruptions this down-rush in one part of the 

 solar atmosphere and- up- rush in another contribute to 

 the permanent maintenance of the solar light and heat. It 

 must be understood that these outbursts are only visible to 

 us as luminous prominences during the period of their 

 explosive outburst, and while still subject to great expan- 

 sive tension. Long after they have ceased to be visible to 

 us their expansion must continue, 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 thousands of miles 

 above the photosphere, according to the magnitude of the 

 ejection. The spectroscopic researches of Frankland and 

 Lockyer having shown that the atmospheric pressure at 

 about the outer surface of the photosphere does not far ex- 

 ceed 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 velo- 

 city of about 450,000 miles per twenty four hours. 



What must be the consequence of this motion ? The sun 

 will carry its own special atmospheric matter with it; but 

 it cannot thus carry the whole of the interstellar medium. 



