OBSERVATIONS OF LUMINOUS METEORS. 399 



drift " as the sun, and some aerolites and fireballs as derived from more 

 distant regions of the fixed stars, the direction and speed of whose motions in 

 space (as gathered from the recent researches of Dr. Huggins and Mr. Proctor) 

 resemble each other, but differ considerably fronl those of the sun. As 

 examples of hj^Dcrbolic velocities among firebalLs and aerolites are of rather 

 rare occurrence, it is, however, admissible to regard these instances as 

 exceptional cases, and not as the normal representatives of their class*. In 

 that case aerolites, as well as shower-meteors, may be parts of cometarj 

 systems ; and it is not impossible that the extraordinary meteorological 

 changes which comets undergo from the excentricities of their orbits, may, 

 by the process of a kind of ' weathering,' disintegrate their surfaces suffi- 

 ciently to scatter such bodies in crowds along their pathsf. In this view, 

 instead of presupposing the existence of cosmical clouds containing all these 

 several bodies separately formed, comets may be regarded as parent bodies, 

 from which aerolites and shower-meteors are similarly derived. Adopting a 

 special theory of the origin and of the physical constitution of comets, 

 Zcilluer explains the production of such star-showers as that which was wit- 

 nessed last November, by a process very similar to the lastj:. Supposing the 

 remnants of a shattered star or planet to be scattered by some catastrophe 

 into intrastellar space, besides the materials of aerolites and detonating fire- 

 balls which would result, it may be assumed that fluid masses, as of their 

 seas (and possiblj^ hydrocarbons) and other easily volatilizable substances 

 would occur among the debris of such a shock. Among the fluids and easily 

 vaporizable materials thus ushered into space, and there maintained as 

 liquids or solids by cold, and by their own attractions, the sun's heat acting 

 upon their otherwise fixed masses, when first drawn into its immediate 

 neighbourhood, would effect a surface distillation sufficiently abundant to 

 detach some vaporous portions from their spheres, or even to volatilize them 

 completely, and to efface them after many periodic revolutions fi-om the sky. 

 These vapours might possibly recondense afterwards into solid dust or drops, 

 to assume the form of meteor-streams along the cometary orbit, producing 

 on their collision with the earth's atmosphere, the extraordinary phenomena 

 of star-showers§. In accepting such explanations of their origin, it must be 

 borne in mind that the streams of meteor-particles with which some periodic 

 comets are associated are altogether differently constituted from the tails and 

 envelopes of such comets, in obeying, as far as has yet been discovered, 

 without any deviations like the extraordinary exceptions which those appen- 

 dages present, the simple law of imiversal gravitation M'hich governs the 



* Scbiaparelli, ' Entwurf einer Astronomischen Theorie der Sternschnuppen ' (Stettin, 

 1871), pp. 207-210, and 216-229. 



t Ibid. pp. 212-13. 



I F. ZoUner, " Ueber den zusammenhang von Sternschnuppen und Cometen," Poggen- 

 dorff's Annals, vol. cxlviii. pp. 322-29. See also ' Ueber Die Natur der Cometen ' (Leip- 

 zig, 1872), by tbe same autbor, p. 109. 



§ Tbat even mineral substances are gradually volatilized at comparatively low tempera- 

 tures, and sublime or are recondensed in appreciable quantities, is sbown by some remark- 

 able experiments by the Eev. W. Vernon Harcourt on various minerals placed for many 

 years imder the hearth of an iron smelting-furnace, as described in the volume of these 

 Eeports for 1860, p. 175 ef. acq. (with coloured plates). Under the action of a prolonged 

 heat, in which neither copper, zinc, lead, nor tin were melted, the oxide of copper which 

 formed a crust upon the plate of that metal, had sublimed, and deposited itself in red 

 crystals along with sublimed metallic copper, not only upon the surface, but also in the 

 interior of the neighbouring piece of lead. The adjacent pieces of the other metiils were 

 similarly calcined, and coated with a thick crystalline crust of their o.xides which bad 

 diffused itself in a similar manner among the substances of the surrounding blocks (see 

 the explanation of the experiments and of the plates, at pp. 188 and 192 of that Report). 



