Obfervathns on Vtre Balls. 75 



entirely difappeared. This divifion alfo feems to oppofe the 

 hypothefis of a traft of inflammable air fet on fire*, which 

 Dr. Chladni has fufficiently refuted on other grounds. 



17. This burfting into pieces was for the mod part ac- 

 companied with a rumbling noife like thunder, or a fudden 

 report. This was obferved to be the cafe in regard to 37 of 

 the 50 above mentioned ; and very often two or more reports 

 .have been heard in fucceffion, without the large ball being 

 divided into fmaller ones, and without thefe being ftill 

 farther mattered. But as thefe reports were heard at a very 

 great diftance f, and as many which did not appear to be 

 more remote, but nearer, have burft without any report ; a 

 queftion a riles, whether we are to confider, as Dr. Chladni 

 does, this violent burfting as peculiar to all thefe phenomena? 



18. Several, after burfting, feemed to diffolve inlo fmoke J, 

 and, according to the obfervation made by Celfius in the 

 month of March 1731, a vifible fmoking (tripe feemed to be 

 previoufly inflamed. The greater part of them, however, 

 after exploding, left no vifible traces behind. 



19. In fome cafes, after their difappearance, a fulphureous 

 fmell was perceived §, like that perceived after lightning has 

 fallen, and which gave occafion to Mufchenbroek's hypothefis 

 of an accumulation of fulphureous inflammable vapours that 

 arife from volcanoes and fubterranean pits, and being driven 

 together by the winds form clouds, that by fome accident or 

 other are fet on fire; but which, however, can as little be 

 reconciled with their general prodigious height, as Silber- 

 fchlag's oily and flimy vapours. 



* Gehlers Phyf. Wbrterbuch, art. Feuerkugel. 



+ Allgem. Hiftorie der Reifcn, vol. ix. p. 564; and Philofoph. Tranf- 

 adions, vol. iii. part 1. p. 1 63. 



+ DcBonon. Scicnt. Inftit it. Comment, vol. i. p. 285; Philofoph. Tranf- 

 attions, vol. xli. part 2. p. S70, vol. xlii. p. 1 ; and Hill, de 1'Acad. des 

 Sciences, Paris 1753, p. 73. 



§ Brcflauer Sammlungcn, i. p. 15^; Philofoph. Tranfa£lions, vol.1. 

 p. 199 ■, and Goih. Magazin, vol. xi. part z« p. 112. 



20. As 



