VOL. LXXIV.] PHILOSOPHICAL TRANSACTIONS. 527 



above the surface of the earth, after all proper allowances are made, must have 

 been between 40 and 50 miles. 



As there was no appearance of bursting at the extinction of this fire-ball, so 

 no report was heard after it ; nor did any sound attend it. Some observers thought 

 this meteor also near as large as the moon, but to Dr. B. it did not appear above 

 one quarter of her diameter, which would make its breadth somewhat above a 

 furlong. If the whole of the meteor's track be included, it seems to have lasted 

 as much as 3 seconds, but in the bright state its duration was less than 2, he 

 thinks not much above 1. Supposing it described an arc of 14° in 14 second, 

 or, according to Mr. Aubert's observation, of 25° in 3 s , its real velocity was 

 about 12 miles a second. 



Such meteors as these, which pass like a flash of lightning, and describe so 

 short a course, are very unfavourable for calculating the velocity, but afford 

 great advantages for determining the height, as they must be seen nearly at the 

 same moment and in the same place by the different observers. Other instances 

 are found of fire-balls beginning with a dull red light like a falling star, particu- 

 larly the great one of March 1Q, 17 19» treated of so fully by Dr. Halley* and 

 Mr. Whiston.-}- It is remarkable, that a similar meteor had appeared the same 

 day, that is, Saturday the 4th of October, about 3 in the morning, though, on 

 account of the early hour, it was seen by fewer spectators. They represent it as 

 rising from the northward to a small altitude, and then becoming stationary with 

 a vibratory motion, and an illumination like day-light ; it vanished in a few 

 moments, leaving a train behind. This sort of tremulous appearance has been 

 noticed in other meteors, as well as their continuing stationary for some time, 

 either before they began to shoot forward, or after their course was ended. 



I find it impossible to quit this subject, says Dr. B., without some reflections 

 about the cause, that can be capable of producing such appearances at an elevation 

 above the earth, where, if the atmosphere cannot absolutely be said to have 

 ceased, it is certainly to be considered as next to nothing. The first idea which 

 suggested itself, that they were burning bodies projected with such a velocity, 

 was quickly abandoned, from the want of any known power to raise them up to 

 that great height, or, if there, to give them the required impetus ; and the 

 ingenuity of Dr. Halley soon furnished him with another hypothesis, in which 

 he thought both these difficulties obviated. He supposes there is no projection 

 of a single body in the case ; but that a train of combustible vapours, accumu- 

 lated in those lofty regions, is suddenly set on fire, whence all the phenomena 

 are produced by the successive inflammation.;}; But Dr. Halley gives no just 



* Phil. Trans., vol. 3, N° 350, p. 978. t Account of a surprizing meteor seen March 19 P 

 1719.— Orig. X Phil. Trans., vol.30, N° 360, 



