﻿252 Chevalier W.*von Haidinger on the Luminous, Thermal, 



certainly an authority in physical questions, expressly asserts, 

 with reference to the phenomena in Geissler's tubes, that " there 

 is no electrical light in the abstract sense of the term," and that 

 " the particles of the gaseous substances become incandescent." 



At the moment when the cosmical velocity, as well as light 

 and heat, is exhausted, the tension of the vacuum within the 

 igneous globe, entirely depending on this velocity, comes to an 

 end, and the meteor obeys only the law of gravitation, causing it 

 to fall on the earth's surface. 



b. Acoustic Phenomena. — The sudden irruption of the sur- 

 rounding atmosphere into the vacuum of the igneous globe 

 causes a violent sound, in the same way as when gunpowder 

 explodes, or whenever longitudinal oscillations take place. One 

 or more detonations are heard, sometimes at intervals, the last 

 one being the most intense. If previously masses, or groups 

 of meteoric swarms, have separated from each other, repeated 

 detonations may be expected. At all events these phenomena 

 still require repeated and close observation before general con- 

 clusions can be founded on them. As we have seen above, Pro- 

 fessor Daubree (p. 16) declared it impossible for him to give a 

 sufficient explanation of the detonations, and acknowledged the 

 special difficulty offered by successive detonations, suggesting the 

 idea of successive discharges and "recharges" of what he terms 

 the " appareil explosif." It is, indeed, impossible to explain a 

 phenomenon having no real existence ; the subject of explana- 

 tion can only be the " detonations " connected with the fall of 

 meteorites that have reached the terrestrial atmosphere, the 

 term of their cosmical career. 



Ad 7. Compensation of temperature takes place between the 

 internal nucleus and the external surface. 



Without doubt the meteorites, before reaching the terrestrial 

 atmosphere, take their course through a space of intensely cold 

 atmosphere*. Professor Daubree (p. 8) explains by this cir- 

 cumstance how the meteorites of Orgueil, containing substances 

 easily alterable by heat, could reach the terrestrial surface with- 

 out alteration of their chemical constitution. The incandescence 

 of the enamelled crust during its formation is likewise not to be 

 doubted. The efficient cause of this high temperature ceases as 

 soon as the meteorite has become stationary. During its sub- 

 sequent fall to the surface time is left for a compensation between 

 the melting temperature of its crust and the intense cold of 

 its nucleus ; and generally fallen meteorites are warm, but not 

 incandescent. Some meteoric irons (as at Caritas Paso in Cor- 

 rientes, 1844) have been found incandescent in their interior — 

 an apparent exception, to be explained by the high thermal con- 

 * Von Haidinger in Vienna Acad. Proc. vol. xxxiv. p. 11, January 7, 1859. 



