526 PHILOSOPHICAL TP.ANSACTIONS. [ANNO 1784. 



45 seconds he observed it, which gives a velocity of more than 20 miles in a 

 second. Finally, Mr. Aubert, f. r. s. thought it described an arch of 136 of 

 azimuth in 10 or 12 seconds, which would make its velocity above 40 miles in a 

 second. Dr. B. is sensible of the objections that may be made to all these com- 

 putations ; undoubtedly they are too vague ; and yet, all taken together, per- 

 haps they may have some weight, especially as they correspond so well with the 

 different phenomena of the meteor's duration, and other fire-balls have been 

 computed to move as fast. Stating the velocity at the lowest computation of 

 20 miles a second, it exceeds that of sound above 90 times, and begins to ap- 

 proach toward that of the earth in her annual orbit. At such a rate, it must 

 have passed over the whole island of Great-Britain in less than half a minute, and 

 might have reached Rome within a minute afterwards, or in 7 minutes have 

 traversed the whole diameter of the earth ! From this calculation it will be 

 evident, that there is little chance of determining the velocity of meteors from 

 the times of their passing the zenith of different places ; and that therefore we 

 must principally depend on observing carefully, with a watch that shows seconds, 

 their apparent velocity through the heavens. 



The fire-ball which appeared Oct. 4, at 43 m past 6 in the evening, was much 

 smaller than that already described, and of much shorter duration. It was first 

 perceived to the northward as a stream of fire, like the common shooting stars, but 

 large ; and having proceeded some way under this form, it suddenly burst out 

 into that intensely bright bluish light which is peculiar to such meteors. At this 

 period Dr. B. saw it, and could compare the colour to nothing so well as to the 

 blue lights of India, and some of the largest electrical sparks. The illumination 

 was very great ; and on that part of its course where it had been so bright, a 

 dusky red streak or train was left, which remained visible perhaps a minute even 

 with a candle in the room, and was thought by some gradually to change its 

 form. Except this train, he thought the meteor had no tail, but was nearly a 

 round body, or perhaps a little elliptical. After moving not less than 10° in this 

 bright state, it became suddenly extinct, without any appearance of bursting or 

 explosion. This meteor was seen for so short a way, that it was scarcely possible 

 to determine the direction of its course with accuracy ; but as in proceeding to 

 the eastward it very perceptibly inclined towards the horizon, it certainly moved 

 somewhere from the north-westward to the south-eastward. Its duration was so 

 short, that many persons thought it passed in an opposite direction ; for his own 

 part, he found himself absolutely unable to determine whether the motion was 

 from or toward the s. e. Some spectators were of opinion, that it changed its 

 course the moment it became bright, proceeding no longer in the same straight 

 line; but his information was not sufficient to determine this question. From 

 his own and another observation Dr. B. calculates that the height of the meteor 



