METEORIC STONES AND SHOOTING STARS. 



nine miles in length), they placed themselves at its extremi- 

 ties, on appointed nights, and observed all the shooting-stars 

 which appeared, tracing their courses through the heavens on 

 a celestial map, and noting the instants of their appearances 

 and extinctions by chronometers previously compared. The 

 difference of the paths traced on the heavens afforded data for 

 the determination of the parallaxes, and consequently the heights 

 and the lengths of the orbits. On six evenings, between Sep- 

 tember and November, the whole number of shooting-stars seen by 

 both observers was 402 : of these, 22 were identified as having 

 been observed by each in such a manner that the altitude of the 

 meteor above the ground at the instant of extinction could be 

 computed. The least of the altitudes was about 6 English 

 miles. Of the whole, there were 7 under 45 miles : 9 between 

 45 and 90 ; 6 above 90 ; and the highest was above 140 miles. 

 There were only two observed so completely as to afford data 

 for determining the velocity. The first gave 25 miles, and the 

 second from 17 to 21 miles, in a second. The most remarkable 

 result was, that one of them, certainly, was observed not to fall 

 but to move iii a direction away from the earth. 



By these observations, a precise idea was first obtained of 

 the altitudes, distances, and velocities, of these singular meteors. 

 A similar but more extended plan of observation was organised 

 by Brandes, in 1823, and carried into effect at Breslau and the 

 neighbouring towns, by a considerable number of persons, 

 observing at the same time on concerted nights. Between April 

 and October, about 1800 shooting-stars were noted at the diffe- 

 rent places out of which number 62 were found which had 

 been observed simultaneously at more than one station, in such 

 a manner that their respective altitudes could be determined, 

 and 36 others of which the observations furnished data for 

 estimating the entire orbits. Of these 98, the heights (at the 

 time of extinction) of 4 were computed to be under 15 English 

 miles ; of 15, between 15 and 30 miles ; of 22, between 30 and 

 45 ; of 33, between 45 and 70 ; of 13, between 70 and 90 ; and of 

 11, above 90 miles. Of these last, 2 had an altitude of about 140 

 miles, 1 of 220 miles, 1 of 280, and there was 1 of which the 

 height was estimated to exceed 460 miles. 



On the 36 computed orbits, in 26 instances the motion was 

 downward, in 1 case horizontal, and in the remaining 9 

 more or less upward. The velocities were between 18 and 36 

 miles in a second. The trajectories were frequently not straight 

 lines, but incurvated, sometimes in the horizontal and sometimes 

 in the vertical direction, and sometimes they were of a serpen- 

 tine form. The predominating direction of the motion of the 

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