272 eepobt — 1878. 



of St. Omer, in France, or in lat. 50° 45' N. ; long. 2° 0' B., the total 

 length of the path being 78 miles + 5 miles. 



The radiant point is obtained with precision in 285° + 64° (neglecting 

 the slight zenithal deflection, the Right Ascension being certainly -within 

 1°, the Declination within 5°), corresponding to 340° of longitnde and 7° 

 of ecliptic North Polar distance. 



The other elements required are — 



o / 



Longitude of the sun 245 50 



Longitude of the apex of the earth's 



motion 156 25 



Log. radius vector 9-99394 



Earth's orbital velocity 19-1 statute miles per second. 



Now assuming, as usual, the meteor to have been moving with the 

 velocity due to a sensibly parabolic orbit — that is to say, 19 - 1 X V 2, 

 the aberration of the radiant would have been 44° 35', and the relative 

 velocity 16 - 9 miles per second. The meteor then would have traversed 

 the 78 miles of its visible path in about 4^ seconds of time, or the 50 

 miles of it seen by Mr. Corder in less than 3 seconds. Altering the 

 position of the radiant, even as much as 10° in the direction of maximum 

 effect, i.e., away from the apex of the earth's motion, produces no sen- 

 sible effect upon this " parabolic " duration. 



The actual duration was certainly not less than 15 seconds ; it may 

 have been 20 seconds (I should say it was 17 seconds, for I frequently 

 test my habit of counting seconds, and generally find it about 5 per cent, 

 too slow.) It is impossible that I can have been many seconds in error 

 in counting 15 or 20. Mr. Corder was struck by the long duration. He 

 made no attempt to count it, as he tried to call the attention of a friend. 

 His rough estimate of 5 or 6 seconds refers to about two-thirds of the 

 visible path. 



Taking 15 seconds as the real duration, the relative velocity is only 

 5£ miles per second, corresponding to an orbital velocity for the meteor 

 of 20'4 miles per second. Since the radius vector is common to both 

 orbits, we have the relation — 



V 1 V = «{v 1 =-V=(2-p)} 



where V„ V are the orbital velocities of the earth and the meteor re- 

 spectively, a the mean distance of the meteor's orbit, that of the earth 

 being 1, and p the common radius vector. 



Whence a = 1-1691, corresponding to the periodic time 462 days, 

 and the other elements of the orbit are — 



q = -9858 

 e = -1568 

 <f> = - 4° 16' 

 ■k = 70° 6' 

 a = 245 50 

 i = 15 

 Motion direct. 



I will now suppose that the actual duration was only one-half of that 

 taken before, that is only 7^ seconds. As the radiant point is determined 

 with a degree of accuracy that will not allow it to be shifted many degrees 

 farther away from the apex, the true orbital velocity of the meteor, on 



