Chap. 9-] of the Atmofphere. 437 



appearance fimilar to thefe, though vaflly inferior in 

 fize, have been fometimes obferved at the furface of 

 the earth. Of this kind, one was feen on board the 

 Montague, 4th November, 1749, which appeared 

 as big as a large millftonej it broke with a violent 

 explofion. 



f From analogical reafoning, it feems very probable 

 that the meteors, which appear at fuch great heights 

 in the air, are not efTentially different from thofe which, 

 like the fire-ball juft mentioned, are met with on the 

 furface of the earth. The perplexing circumflances 

 with regard to the former are, that at the great heights 

 above-mentioned, the atmofphere ought not to have 

 any denfity Jufficient to Jupport flame, or to -propagate 

 found; yet thefe meteors are commonly fucceeded by 

 one or more explofions, nay, are fometimes faid to be 

 accompanied with a hifllng noife as they pafs over 

 pur heads. The meteor of 1719 was not only very 

 bright, infomuch that for a fhort fpace it turned night 

 into day, but was attended with an explofio'n, heard 

 over all the ifland of Britain, occafioning a violent con- 

 cuffion in the atmoiphere, and feeming to (hake the 

 earth itfclf. That of 1783 alfo, though much higher 

 than the former, was fucceeded by explofions ; and, 

 according to the teftimony of feveral people, a hifling 

 noife was heard as it paffed. Dr. Halley acknow- 

 kdged, that he was unable to reconcile thefe circum- 

 ftances with the received theory of the height of the 

 atmofphere; as, in the regions in which this meteor 

 moved, the air ought to have been three hundred 

 thoufand times more rare than what we breathe, and 

 the next thing to a perfect vacuum. 



f In the meteor of 1783, the difficulty is ftill 

 greater,' as it appears to have been twenty miles far- 

 ther up in the air. Dr. Halley offers a conjecture, 

 F f 3 indeed, 



