prevale7it Disorders, Sj-c, with Volcanic Emanations, 613 



want of space, to be compressed and abbreviated. The great 

 question of the origin of these meteors is considered, I must 

 say, fairly; but the solution is totally at variance with a vol- 

 canic hypothesis. The first argument is, that, if the meteors 

 were " atmospheric, electrical, magnetic, or even unknown and 

 merely imaginable,^^ they ought to have conformed, in arrange- 

 ment or motion, to geodesic lines. But, with all deference to 

 the reasonings of Mr. Twining and Professor Olmsted (who 

 has considered gravity " an adequate cause " of the motions, 

 in which I agree with him ; though Mr. Twining disputes it), 

 it does not at all follow that meteors occasioned by volcanic 

 emanation should pursue any " geodesic " line. If their com- 

 posing matter had been pumped upwards into great heights, 

 in or above what is called " our atmosphere," they might, 

 after having been, either by attraction or electrical forces, 

 formed into a mass, be whirled along by the action of wind ; 

 or might partake of the earth's proper motion, through 

 restraint of gravity, and appear to have an eastward motion ; 

 till, becoming stationary, they should be discharged as de- 

 scribed, the stationary position being determined by the excess 

 of gravity. I cannot but infer that this position of the radiant 

 is a powerful argument in favour of a terrestrial origin. It 

 may also be added, that a want of coincidence with the mag- 

 netic dip and variation is not a reason why these meteors had 

 nothing in common with the " north lights " or the auroral 

 arch; for, though the aurora has frequently (p. 291.) corre- 

 sponded in these respects, it has not always corresponded; 

 and the absence of agitation on the part of the needle, during 

 the display (as noticed by Mr. Twining in his " investigation ; " 

 Silliman's Journ., July, p. 347.)5 is not a necessary absence ; 

 for the needle is not always affected by the aurora, though 

 there are cases where such has been the effect.* Mr. Twining 

 contradicts himself when he says, " the reverse of such a 

 coincidence do we find ; " for he has allowed some " parti- 

 cular accidental coincidences," which, perchance, were not 

 accidental. Moreover, it has been before stated, in the Ame- 

 rican Journal (xxv. 356. : see M, N. H., vii. 291.), that the 

 radiant agreed exactly with the point of magnetic direction ; 

 and the whole evidence goes to prove that the cessation of 

 progressive motion corresponds with this point. The change 

 of declination of the meteors (Mr. Twining allows) may turn 

 the argument against him : it certainly does so, and by no 

 means encourages the supposition that " any terrestrial origin 

 seems to be cut off." {Sil. J. p. 347.) The next argument is, 



* Arago noticed it on Feb. 7. 1831 ; and Faraday and Christie, on 

 April 19. 1831. {Report of the British Association.) 



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