OBSERVATIONS OF LUMINOUS METEORS. 85 



radiant-point whose celestial position was at 133° + 19°, and whose ap- 

 parent place for the horizon of Rakonitz at the time of the meteor's 

 apparition was about E.N.E. alt. 14 . 1 Mr. Denning's January shower 

 of ' Cancrids' (December 21-January 5, 130° + 20°), and the comet of 

 1680 (December 26, 132° + 21- 5°), 2 together with the fireball of January 

 19, 1877, seen in England, Wales, and Ireland, 3 all present radiant- 

 points with which this new detonating fireball's real point of departure 

 was thus found to be nearly concentric in position. 



Although doubtless visible (as some of the descriptions show) at a 

 much earlier period of its flight, the first point at which the fireball's 

 course was well observed, and for which the time of flight was also noted, 

 was at a height of 41 miles above the earth's surface, 125 miles from the 

 end-point of its track. This distance it traversed in 5 seconds ; and 

 shorter lengths of the latter part of its flight were seen to be traversed, 

 by five other observers, in times varying from 2\ to 5 seconds. The 

 meteor's mean velocity at last, from all these estimates, was 17 miles per 

 second; while that of the fireball of January 19, 1877 (scarcely so 

 well determined) was not less than 35 miles per second. The parabolic 

 speed of meteors from this radiant-point is 23 miles per second, which is 

 intermediate between these two observed velocities. 



The near approach of this fireball's luminous track to the earth's 

 surface is a rare and remarkable feature of the above described results of 

 its appearance, and it is very certainly determined. The depth to which the 

 igneous mass of the meteor penetrated the atmosphere accounts at once, 

 as Professor von Niessl conjectures, for the violence of the explosion, and 

 for the moderate velocity with which it appears at last to have been tra- 

 versing the air. The same condition of unusually deep penetration he con- 

 siders may also have occasioned the remarkably slow'relative velocity of the 

 fireball of November .27, 1877, whose end-height Major Tupman found to 

 be only 14 miles, and" whose velocity relative to the earth he showed not 

 to have exceeded 5 miles per second, answering in the visible part of that 

 fireball's flight to a very short elliptic, and nearly circular orbit round 

 the sun. 



It may be noticed here that a remarkable resemblance of the latter 

 fireball's real orbit to that of Biela's comet was pointed out by Mr. Hind, 

 of which the following particulars, here transcribed in full, appeared in 

 * Nature,' vol. xix. p. 484, March 27, 1879. 



' Captain Tupman thinks the radiant-point was pretty accurately 

 determined in R.A. 285°, Decl. + 64°, or in longitude 340°, and lati- 

 tude + 83°. The elements of the real orbit which, with the aid of the 

 other corresponding data depending upon the earth's position in her 



1 With the omission of one discordant estimate, at Prague, of the meteor's appa- 

 rent slope of path, a better defined position of the radiant-point, at 132° + 21°, would 

 be obtained, Professor von Niessl shows, presenting an even closer agreement than 

 the adopted place with the above-quoted radiant-points. 



2 See a note of this accordance of the comet with Denning's meteor shower in 

 these Eeports, vol. for 1877, p. 167. 



3 These Reports, vol. for 1877, pp. 118, 153 ; and vol. for 1878, p. 267 (where the 

 shower D8, 1877, is erroneously indicated as the < Cancrid ' system, with which the 

 fireballs radiant-point appears to have been concentric). Professor von Niessl has 

 also re-computed the real path of the fireball of January 19, 1877, from its descrip- 

 tions ; and has obtained a position of its radiant -point at 135°-5 + 22°, instead of at 

 135° + 27° ( ± 6°), the place assigned to it in the Monthly Notices of the Royal Astro- 

 nomical Society, vol. xxxviii. p. 228, and xxxix. p. 281, and in the place here quoted, 

 where its real path was first investigated, in these Reports. 



