﻿and Acoustic Phenomana attending the Fall of Meteorites. 249 



explanation made easier. The first proposition may be expressed 

 more precisely thus : A fragment (or a group of fragments) in its 

 course meets the limits of the terrestrial atmosphere. 



Ad 2. The cosmical velocity of the fragments meets resistance, 

 and consequently is diminished. — This proposition is certainly 

 not subject to any objection. 



Ad 3. Together with the diminution of velocity, the compres- 

 sion of the air developes light and heat, the meteorite takes a rota- 

 toy movement, and an enamelled crust forms on its surface. 



Ad 4. The heated stratum of air, due to the pressure of the me- 

 teorite deprived of its cosmical velocity, is pushed forward in pro- 

 portion to the initial force of movement, and agglomerates behind it 

 in an " igneous globe." 



a. Luminous Phenomena. — The ideal diagrams (figs. 1 and 2) 

 may assist in the explanation of these phenomena. Pressure pro- 

 duces a centre of expansion in front of the meteorite. The corn- 

 Fig. 1. 



Fig. 2. 



pressed air is forced out of it radially in every direction. The re- 

 sistance remains equal against this luminous disk ; only at some 

 distance in the direction of the line of course it overcomes the lu- 

 minous and incandescent stratum of air, pressing it at last behind 

 the course of the meteorite. Movement is transmuted into light 

 and heat — a proposition frequently enunciated of late years, and 



