392 Mr Galloway on Shooting-Stars and Meteors. 



proach the region of space through which the earth is moving, 

 they enter the3atmosphere with great velocity, and by reason 

 of the resistance and friction are rendered incandescent, and 

 emit a vivid light so long as they remain within it. 



3. It has been suggested by Biot that the extraordinary 

 displays observed in November may be explained by suppos- 

 ing the meteors to have their origin in the zodiacal light. 

 The extent of this lens-shaped nebulosity is not well ascer- 

 tained ; but as the plane of its principal section is not parallel 

 to the ecliptic, if the earth passes through it at one season, it 

 must be remote from it at another. But shooting-stars are 

 observed at all times of the year ; and the November meteors 

 differ from those of other seasons in no respect excepting in 

 their greater multitude. 



4. The hypothesis first suggested by Chladni is that which 

 appears to have met with most favour, having been adopted 

 by Arago and other eminent astronomers of the present day 

 to explain the November phenomena. It consists in suppos- 

 ing that, independently of the great planets, there exist in 

 the planetary regions myriads of small bodies which circulate 

 about the sun, generally in groups or zones, and that one of 

 these zones intersects the ecliptic about the place through 

 which the earth passes in November. The principal difficul- 

 ties attending this theory are the following : — First, that 

 bodies moving in groups in the circumstances supposed must 

 necessarily move in the same direction, and consequently 

 when they become visible from the earth, would all appear to 

 emanate from one point and move towards the opposite. Now 

 although the observations seem to shew that the predominat- 

 ing direction is from north-east to south-west, yet shooting- 

 stars are observed on the same nights to emanate from all 

 points of the heavens, and to move in all possible directions. 

 Secondly, their average velocity (especially as determined by 

 Wartmann) greatly exceeds that which any body circulating 

 about the sun can have at the distance of the earth. Thirdly, 

 from their appearance and the luminous train which they ge- 

 nerally leave behind them, and which often remains visible for 

 several seconds, sometimes for whole minutes, and also from 

 their being situate within the earth's shadow, and at heights 



