h% Obfervat'ions on Fire Balls. 



8. They almoft all fell towards the earth, and consequently 

 from a rarer to a denfer atmofphere, as in mod cafes might 

 be concluded from their foon becoming considerably en- 

 larged. Some of them, however, particularly thofe which 

 moved flowly, feemed to proceed in a horizontal direction 

 over the furface of the earth ; but none of them, according 

 to every appearance, moved upwards. Their motion, there- 

 fore, cannot be explained in the fame manner as that of 

 fky-rockets *, where the fuperior air is rarified by the flame, 

 and that below condenfed. 



9. Their form was fometimes perfectly globular, and fome- 

 times more fpindle fhaped ; fo that their length often occu- 

 pied feven or eight degrees of the heavens. When obferved 

 to move with great velocity, they had a long tail behind, 

 which arofc chiefly from the continuance of the impreffion 

 made on the eye f. Others, however J, and particularly 

 thofe which moved flowly, fhewed that a part of the tail 

 belonged to the body itfelf ; and it would appear that the 

 long train which marks their courfe, ought often to be ex- 

 plained rather by traces left behind them than by mere im- 

 preffion §. 



10. Their apparent magnitude was very different, but 

 on feveral occafions greater than that of the moon ||. 



• G> tha'fcl es Magazin, vol. iii. part 2. p. 95. 



f Intelli^imus magis qua appareat ftella, quam qua eat. Itaque velut 

 igric continuo totum iter fignat, quia vifus noftri tarditas non fubfequitur 

 momenta cuirentis, fed videt fimul et unde exfilierit et quo pervenerit. 

 Quod fit in fulmine, longus nobis videtur ignis ejus, quia cito fpatium fuum 

 tranfilit, et oculis noftris ocairrit univerfum, per quod dtjeflus eft. At 

 ille non eft extcnti corporis per omne qua venit. Seneca CLueft. Natur. 

 lib. i. cap. xiv. 



t Robinfon in the Philofoph. Tranfactions for 1784, part i. p. 225. 



§ Breflauer Sammlungen, i. 1717. p. 157; Philofoph. Tranfa&ions, 

 vol.'xli. part 2. p. 870, vol. xlii. p. 1 j and Tranfadlions of the American 

 Philofoph. Society, vol. ii. p. 173. 



|] Hiftoire dc l'Acad. des Sciences. Paris 1761. p. 28. Gothaifchts 

 RIagazin, vol. ii':. rare ii. p. 92. 



II. Only 



