iSyi.] The Fuel of the Sun. 437 



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 

 accepted 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 i-iooth 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 funda- 

 mentally altered since these words were written. We are 

 no longer " left to conjectures founded on the supposed divi- 

 sibility of matter" to determine the possibility of further 

 expansibility than that indicated by i-iooth 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 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 still 

 unable to detect any indication of any limit to its expan- 

 sibility. 



The most remarkable part of Dr. Wollaston's paper is 

 the reductio ad absurdum by which he seeks to finally demon- 

 strate the finite extent of our atmosphere. He maintains, 

 as I do, that if the elasticity of our atmosphere is unlimited, 

 its extension must be commensurate with the universe, that 

 every orb in space will, by gravitation, gather around itself 

 an atmosphere proportionate to its gravitating power, and 

 that, by taking the known quantity of the earth's atmo- 

 sphere as our unit, we may calculate the amount of atmo- 

 sphere possessed by any heavenly body of which the mass is 

 known. On this basis, Dr. Wollaston calculates the atmo- 

 sphere of the sun, and concludes that its extent will be so 

 great as to visibly affect the apparent motions of Mercury 

 and Venus, when their declination makes its nearest approach 

 to that of the sun. No such disturbance being actually 

 observable, he concludes that such an atmosphere as he has 

 calculated cannot exist. In like manner he calculates the 

 atmosphere of Jupiter, and finds it to be so great that its 

 refraction would be sufficient "to render the fourth satellite 

 visible to us when behind the centre of the planet, and con- 

 sequently to make it appear on both (or all) sides at the 

 same time." 



