288 METEOES AND AEEOLITES. 



more earnest in expounding and enforcing the opinion, that 

 asteroids or aerolites are independent portions of matter in 

 space; becoming luminous meteors or projectiles, when their 

 orbits approach within certain distances of that of the earth. 

 He avows, when leaving the subject, that he has lingered 

 upon it with predilection (mit Vorliebe), and the whole course 

 of his argument shows this to be so. Sir J. Herschel, an equal 

 authority, expresses the same view as the only one which 

 comprises, or adequately explains, all the phenomena ; thus 

 confirming the expression of Laplace (in his speech of 

 December 1802) as to aerolites, that ( in all probability they 

 come to us from the depths of the celestial space.' 



There arise out of this theory various physical questions, 

 some of which we cannot omit to notice. One of these res- 

 pects the luminous and ignited condition of meteorites when 

 approaching the earth. Though it seems certain that some 

 alteration of state beyond mere change of direction is pro- 

 duced by this proximity ; and though condensation of the 

 air, from the extreme velocity of falling stones, might 

 doubtless produce the heat, combustion, and explosion at- 

 tending their fall ; yet, from the elevation of many meteors, 

 brilliant in light, above the recognised limits of the atmo- 

 sphere, we are bound to suppose other causes also concerned. 

 Modern science teaches us that ignition (viz. light and heat) 

 occurs in various cases without the presence of air. In this 

 case it may possibly be magnetical in kind ; a supposition 

 authorised by the discoveries of the last few years, which 

 make it probable that this great element is largely engaged 

 even in the astronomical conditions of the universe. The 

 paper recently published by Professor Faraday on the Phy- 

 sical lines of Magnetic Force, while marked by all the 

 modesty of his genius, is profoundly suggestive of relations 

 of this kind yet unexplored ; and of forces pervading space 

 in lines of action differing from any other of which we have 



