THEIR HEIGHTS AND VELOCITIES. 



meteors from north-east to south-west, contrary to that of the 

 earth in its orbit, was very remarkable, and is important in 

 reference to their physical theory. 



6. A similar set of observations was made in Belgium, in 1834, 

 under the direction of M. Quetelet, the results of which are 

 published in the " Annuaire de Bruxelles for 1837." M. Quetelet 

 was chiefly solicitous to determine the velocity of the meteors. 

 He obtained six corresponding observations, from which this 

 element could be deduced, and the result varied from 10 to 25 

 English miles in a second. The mean of the six results gave a 

 velocity of nearly 17 miles per second, a little less than that of 

 the earth in its orbit. 



7. Another set of corresponding observations was made in 

 Switzerland, on the 10th of August, 1838, a circumstantial 

 account of which is given by M. Wartmann in " Quetelet's 

 Correspondence Mathematique for July, 1839." M. "Wartmann 

 and five other observers, provided with celestial charts, stationed 

 themselves at the observatory of Geneva, and the corresponding 

 observations were made at Planchettes, a village about sixty 

 miles to the north-east of that city. 



In the space of seven and a half hours, the number of meteors 

 observed by the six observers at Geneva was 381, and during 

 five and a half hours the number observed at Planchettes by two 

 observers, was 104. All the circumstances of the phenomena 

 the place of the apparition and disappearance of each meteor 

 the time it continued visible, its brightness relatively to the 

 fixed stars, whether accompanied with a tram, &c. were 

 carefully noted. The trajectories described by the meteors 

 were very different, varying from 8 to 70 of angular space. 

 The apparent velocities also differed considerably ; but the 

 average velocity was supposed by M. Wartmann to be 25 per 

 second. It was found, from the comparison of the simultaneous 

 observations, that the average height above the ground was 

 about 550 miles ; and hence the relative velocity was computed 

 to be about 240 miles in a second. But as the greater number 

 moved in a direction opposite to that of the earth in its orbit, 

 the relative velocity must be diminished by the earth's velocity 

 (about 19 miles in a second) ; this still leaves upward of 220 

 miles per second for the absolute velocity of the meteor, which 

 is more than 11 times the orbital velocity of the earth, seven and 

 a half times that of the planet Mercury, and probably greater 

 than that of many of the comets at their perihelion. 



8. Such are the principal facts which have yet been estab- 

 lished respecting the heights, velocities, and orbits of the shooting- 

 stars ; and it is from these, chiefly, that we are enabled to form 



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