CHAP. 3.$ 1. OF METEORS. 119 



SECTION I. 



Of the Causes of the Igneous Meteors, described 

 above. 



VARIOUS have been the conjectures of dif- 

 ferent philosophers about the causes of igneous 

 Meteors: their precise cause has, however, never 

 been ascertained. M. De Luc ascribes them to 

 certain phosphorific exhalations, which ascend 

 from the earth, and take fire or become phos- 

 phorescent in the air.* We shall see how this 

 hypothesis will agree with their kind of motion, 

 their peculiarities, and the kind of weather 

 which precedes, accompanies, or follows them. 



On the above supposition, must we regard 

 them as taking place in the following manner. 

 The exhalation from the earth must be a cir- 

 cumscribed column of some kind of volatile 

 matter, which, when it arrives at a certain 

 elevation, takes fire: this might easily be 



* Nicholson's Journal of Nat. Phil. &c. 1812. 



noticed by Arbuthnot, and by the Abbe Bertholon in his " De 

 L'electricite des Meteors. 8vo. Lyons, 1787, vol. ii. p. 25. 

 Where are some curious observations on the Feux St. Elme, 

 Feux Follets, and other Meteors. 



