﻿248 Chevalier W. von Haidinger on the Luminous, Thermal, 



ing air suddenly rushing into the vacuum within the igneous 

 globe causes a detonation. 



(7) A compensation of temperature takes place between the 

 cold internal nucleus and the external surface. 



(8) The meteorite, now subject to the laws of gravitation, 

 falls on the surface, its temperature standing in direct proportion 

 to the thermo-conductive power of its substance. 



Ad 1. A fragment in its course meets the upper limit of the 

 terrestrial atmosphere. — The existence of but one single frag- 

 ment detached from a larger body is supposed, in order to 

 simplify the reasoning. Two or more fragments moving in the 

 same direction under the impulse of the same force, either 

 in immediate contact or with a greater or less distance be- 

 tween them, may as well be supposed to enter at once the ter- 

 restrial atmosphere. Professor Daubree expresses a different 

 opinion, saying (p. 16), " Nothing entitles us to admit, as it has 

 been asserted, that the different meteorites of the same fall tra- 

 verse cosmical space separated from each other and, as it were, 

 in swarms;'* and (p. 14), "So in general the bolides leave 

 us parts of their substance in three different ways: (1) by 

 combustion, vaporization, or gasification ; (2) by being dis- 

 persed into dust, the fall of which generally escapes observation, 

 and which may be analogous to the dust gathered after certain 

 meteoric falls ; (3) by dispersion of the fragments detached at 

 the moment of the explosion." Further, " The proceedings are 

 such as if the greatest portion of the meteoric mass would pass 

 from the atmosphere to continue its cosmical course, leaving be- 

 hind only some particles whose velocity has been lessened in 

 consequence of the explosion." Professor Daubree admits still 

 another supposition, saying (p. 10), " There is no proof that, 

 besides this sudden exhalation, these small planetary bodies are 

 not endowed with an atmosphere of their own, which indeed 

 they absorb soon after their entrance into our atmosphere. 

 These gaseous substances, whatever may be their origin, may, by 

 their combustion, increase the splendour of the meteor ; how- 

 ever, as they would burn away in continuity^ they leave unex- 

 plained the fact of the explosion preceding any fall of meteo- 

 rites." If Professor Daubree, having entered into the most mi- 

 nute distinctions and called in to aid several very objectionable 

 suppositions, concludes with acknowledging the want of satis- 

 factory explanations for the explosions, it must not be wondered 

 at that M. St. Meunier speaks of their cause as "absolutely un- 

 known." In fact, an "explosion" exists not, and therefore 

 neither admits nor wants explanation. The term itself is im- 

 proper ; and if instead of it the term " detonation " is used (as 

 it ought to be), an inaccurate presupposition is eliminated and 



