SHOOTING STARS. 265 



Oar forefathers had considered that falling stars were of a 

 purely terrestrial nature and originated in the upper limits of the 

 atmosphere by chemical exhalations from the earth. Halley, and 

 afterwards De Luc, adopted this idea, and reasoning upon it 

 managed to account for many facts attending their appearance. 

 The latter imagined that they had their origin in phosphoric fluids 

 ascending from certain parts of the earth's surface, which became 

 visible when, having been decomposed in the upper regions, they 

 had taken fire and the ignition extended itself rapidly backwards 

 to other parts of the column until it came to a portion surrounded 

 by a moisture-laden atmosphere which extinguished it. The 

 resulting appearance would be obviously that of a falling star, and 

 he further sought to establish a connection between them and 

 gales of wind. 



Another theory, attributed to Arago, Laplace and others, was 

 that meteors were ejections from lunar volcanoes, which coming 

 within the power of the earth's attraction, were drawn towards 

 her surface and occasionally fell in metallic masses of which many 

 accounts were on record. But these ideas were not generally 

 accepted though each had a section of adherents. The fact is that 

 men had begun to theorise before they had begun to observe and 

 accumulate facts. They had learnt little or nothing as to the 

 appearances, numbers and directions of falling stars, and therefore 

 had no materials on which to found any satisfactory explanations 

 accounting for them. 



In 1833, however, there was a fine recurrence of that great 

 November meteor shower which had been witnessed by Humboldt 

 and his fellow-traveller Bonpland in 17993 and coming directly 

 under the observation of Olmsted an acute American astronomer, 

 he was led to investigate their nature, and in his work on 

 " The Mechanism of the Heavens,''* he published an able and in 

 parts accurate disquisition upon them. He was led to suppose 

 that meteors were combustible bodies composed of very light 

 materials or they would penetrate the atmosphere and more 



