THE FUEL OF THE SUN. 9 



4. The cause of the varying splendor of the photosphere, 

 including such details as the " faculae," " mottling," " gran- 

 ulations," etc., etc. 



5. The forces which upheave the solar prominences. 



6. The origin of the corona and zodiacal light. 



7. The origin of the meteorites and the asteroids. 



8. The meteorological phenomena of the planets. 



9. The origin of the rings of Saturn. 



10. The origin of the special structure of the nebulae. 



11. The source of terrestrial magnetism, and its connec- 

 tion with solar activity. 



The first and second chapters are devoted to an examina- 

 tion of the limits of atmospheric expansibility. The ex- 

 perimental investigations of Dr. Andrews, Mr. Grove, Mr. 

 Gassiot, and M. Geissler are cited to prove that the expansi- 

 bility of the atmosphere is unlimited, and other cosmical 

 evidence is adduced in support of this conclusion. 



As this, which is really the foundation of the whole argu- 

 ment, is directly opposed to the views expressed by Dr. 

 Wollaston, in his celebrated paper on " The Finite Extent 

 of the Atmosphere," published in 1822, and generally ac- 

 cepted as established science, this paper is reprinted in the 

 second chapter, and carefully examined. 



Dr. Wollaston says "that air has been rarefied so as to 

 sustain l-100th of an inch of barometrical pressure," and 

 further, that " beyond this limit we are left to conjectures 

 founded on the supposed divisibility of matter; if this be 

 infinite, so also must be the extent of our atmosphere." 



I contend that our knowledge of the whole subject is 

 fundamentally altered since these words were written. We 

 are no longer ''left to conjectures founded on the supposed 

 divisibility of matter" to determine the possibility of further 

 expansibility than that indicated by l-100th of an inch of 

 barometrical pressure, as we now have means of obtaining 

 ten times, a hundred times, a thousand times, or even an 

 infinitely greater rarefaction than Wollaston's supposed 

 limit, an apparently absolute vacuum being now obtainable: 

 and although the transmission of electricity affords a means 

 of testing the existence of atmospheric matter with a degree 

 of delicacy of which Wollaston had no conception, we are 



