OBSERVATIONS OF LUMINOUS METEOES. 79 



appearance over the neighbourhood of Belgrade, its height at that point, 

 on the course assigned to it by Professor von Niessl, would be 260 miles, 

 and the total length of its nearly horizontal course was close upon 1200 

 miles ! From the above point of geometrical intersection of the lines of 

 sight, however, the entire length of course is about 1780 miles. 



Professor von Niessl observes that a more southern track, with the 

 same radiant-point, but with a lower termination, 104 miles over Ozaine, 

 near Tours, passing backwards over Belgrade, and thus within 8 or 10 

 miles of the long course assigned to it by M. Tissot, agrees rather better 

 than the calculated one with the general descriptions. The observer's 

 view (Mr. B. F. Smith's) at Puy de Sancy, of the end of the meteor's 

 course, 'exactly at /3 Ursa? Majoris,' 1 gives an end-height, it should be 

 noticed, over Tours, of only 70 miles. But even with this minimum 

 elevation, and with heights over the neighbourhood of Zurich, 400 miles 

 from the place of extinction, variously given by observations as between 

 105 and 150 miles, the height over Belgrade, if we assume the meteor's 

 course to have been rectilinear, and to have begun so soon, cannot have 

 been less than 220 miles. 



Performed in 17 seconds (the time of flight observed at Bergamo by 

 Zezioli), the course of 1200 miles from Belgrade implied a velocity of 70 

 miles per second. Four other observed durations varied from 12 seconds 

 at Clermont Ferrand to two minutes at Zurich, and the average dura- 

 tion from the five accounts, of 42 seconds, gives with the same course a 

 velocity of 29 miles per second. Some 30 or 80 miles of the course 

 (' 20° or 30° ') were again described by Mr. E. Jones as the meteor's rate- 

 of motion ' per second ' at Geneva ; and about 120 miles of the terminal 

 part were observed at Puy de Sancy to be traversed in 4 or 5 seconds, 

 giving a velocity of 25 or 30 miles per second. The parabolic speed of 

 a meteor having the same radiant-point as that which Professor von 

 Niessl has obtained of this large fireball would be 26 miles per second. 

 But the evidence relating to the meteor's real velocity is scarcely certain 

 enough to allow it to be made a subject of useful speculation in compari- 

 son with any theoretical parabolic or other orbital velocity. 



_ It seems probable from this discussion that the fireball passed in the 

 brightest part of its course from about 130 miles over the Lake of Zurich 

 to not much less than 100 miles over the neighbourhood of Tours, 

 crossing the Jura range, and the Swiss and French plains near it at a 

 great height for a distance of 400 miles. An equal distance at least, if 

 not a still larger one, was traversed by the meteor along the valley of the 

 Drave, from a height of little less than 250 miles, near, or in the direction 

 of Belgrade, before crossing the range of Tyrolese Alps about that river's 

 source, and entering Switzerland near the Brenner pass. Professor von 

 Niessl confines himself to presenting the much more startling results 

 obtained directly from exact comparisons of the most precise descriptions ; 

 and by clearly deducing the radiant- point, and fully establishing the 

 meteor's great height, he, in the main, confirms M. Tissot's track, while 

 yet showing that it was almost exactly horizontal at Tours, where the 

 meteor disappeared, instead of at its first origin at Belgrade, as M. Tissot 

 had supposed. 



1873, December 24, 7 h 39 m p.m. (Washington Mean Time). Deto- 

 nating fireball. — A Committee of the Philosophical Society of Washington 



_ ' This star is supposed by Professor von Niessl to have perhaps been accidentally 

 mistaken for the upper one, a of the two ' pointers ' in Ursa Major. 



