74 SCIENCE IN SHORT CHAPTEKS. 



1. The sources of solar and stellar heat and light. 



2. The means by which the present amount of solar heat 

 and light must be maintained so long as the solar system con- 

 tinues in existence. 



3. The origin of the general and particular phenomena of 

 the sun-spots. 



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

 including such details as the ** faculse," " mottling," " granu- 

 lations," etc., etc. 



5. The forces which upheave the solar prominences. 

 G. The origin of the corona and zodiacal light. 



7. The origin of the meteorites and the asteroids. 



8. The meteorological phenomena of the planets. 

 0. 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 connection 

 with solar activity. 



The first and second chapters are devoted to an examination 

 of the limits of atmospheric expansibility. The experimental 

 investigations of Dr. Andrews, Mr. Grove, Mr. Gassiot, and 

 M. Geissler arc cited to prove that the expansibility 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. 

 AVollaston, in his celebrated paper on ** The Finite Extent of 

 the Atmosphere," published in 1822, and generally accepted 

 as established science, 1his paper is reprinted in the second 

 chapter, and carefully examined. 



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

 sustain 1-1 00th of an inch of barometrical pressure," and 

 further, that 4t 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 funda- 

 mentally altered since these words were written. We are no 

 longer " left to conjectures founded on the supposed divisibil- 

 ity of matter" to determine the possibility of further expansi- 

 bility 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 



