﻿and Acoustic Phenomena attending the Fall of Meteorites. 253 



ductive power of iron. In the report on the meteoric fall of 

 Dhurmsala (India) some fragments are said to have been " in- 

 tensely cold." Conceivable as this fact may be, meteorites 

 having undergone the intense cold of cosmical space before their 

 arrival in the earth's atmosphere, it is a new proof with what 

 caution facts must be ascertained and asserted by future obser- 

 vers : in the first, superficial reports on the fall of Knyahynia 

 in Hungary (July 9, 1866), the meteorites were said to have 

 been as cold as ice ; further inquiries elicited that the few speci- 

 mens collected immediately after the fall had been of no higher 

 temperature than any other stones exposed to the sun for some 

 time would be. 



Ad 8. The meteorite, now subject to the law of gravitation, 

 falls on the surface, its temperature being in direct proportion to 

 the thermo -conductive power of its substance. — This proposition, 

 being a necessary corollary of proposition 7, requires no special 

 discussion. 



The enamelled crust of meteorites offers some peculiarities, 

 among which one is important enough to deserve special notice. 



c. Seams of enamelled crust. — These seams are eminently 

 conspicuous on the meteorites of Orgueil and of Stannern. 

 Von Haidinger* admits that any meteoric fragment of some- 

 what regular figure, having entered the limit of the terres- 

 trial atmosphere, persists in one and the same direction, de- 

 termined by its figure, during the period whilst its enamelled 

 crust is forming, and that the differences shown by this crust 

 depend on the position of the surface-planes of the meteorite — 

 the anterior plane being surrounded by a characteristic seam 

 of enamelled crust, distinguishing it from the lateral and 

 posterior planes. Professor Daubree acknowledges also two 

 forms of crust, which, as he says (p. 6), may serve to indicate 

 the direction of the meteorite's course ; but he submits (p. 7) that 

 " the meteorites showing both varieties of crust have undergone 

 two successive superficial fusions during their atmospheric course 

 — at first a general one of the whole substance, perhaps connected 

 with the heat attending the explosion, then a greater degree of 

 fusion on the portion pressing before it the air with an intensity 

 proportional to the enormous velocity of movement. " He sup- 

 poses evidently an explosion to be the first cause of the forma- 

 tion of a crust; while von Haidinger thinks the detonation indi- 

 cative of the final moment, when the meteorite, with its crust com- 

 pletely formed, becoming stationary, and the emission of light 

 having ceased, falls to the surface of the earth just as any other 



* Acad. Vienna Proc. vol. xl. pp. 525-536, April 19, I860, and vol. 

 xliv. (2) pp. 790-795, May 16, 1862. 



