METEORIC STONES AND SHOOTING STARS. 



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

 locity 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 1 1 times the orbitual 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. 



Such are the principal facts which have yet been established respecting the 

 heights, velocities, and orbits, of the shooting stars : and it is from these, 

 chiefly, that we are enabled to form any probable conjectures respecting their 

 origin. And since it is now established that no difference is observable be- 

 tween the larger shooting stars and small fire-balls, both having similar altitudes 

 and velocities, and presenting absolutely the same appearances, we may as- 

 sume them to be of the same nature, and that whatever has been proved re- 

 specting fire-balls will apply equally to the larger shooting stars. Whether 

 the meteoric appearances to which the latter term is applied may not include 

 objects of totally different natures, is a question admitting a doubt. It is possi- 

 ble that among the shooting stars there may be objects which are merely electric 

 sparks, or which have their origin in spontaneously-inflammable gases, known 

 or unknown, existing in the atmosphere ; but the greater part of them must be 

 considered as identical with fire-balls. 



The lunar hypothesis advanced by Laplace, Berzelius, and others, to ex- 

 plain meteoric stones, appears to be attended with serious difficulties, if, in- 

 deed, it be not altogether incompatible with the phenomena of shooting stars. In 

 order to enter our atmosphere with a velocity of 20 miles in a second, it may 

 be shown that, if they come from the moon, they must have been projected from 

 the lunar surface with a velocity of about 120,000 feet, in a second, which may 

 be regarded as almost impossible. 



It thus appears that those shooting stars and fire-balls which have the plane- 

 tary velocity of from 20 to 40 miles in a second, cannot, with any probability, 

 be regarded as having their origin in the moon. Whether any individual bod- 

 ies, moving with a smaller velocity, may have a lunar origin, is a question 

 ( which cannot be decisively answered. "To me," says Dr. Olbers, "it does 

 ) not appear at all probable ; and I regard the moon, in its present circumstan- 

 i ces, as an extremely peaceable neighbor, which, ftom its want of water and 

 y atmosphere, is no longer capable of any strong explosions." 

 I The hypothesis first suggested by Chladni is that which appears to have 

 ) met with most favor, having been adopted by Arago and other eminent astrono- 

 ( mers of the present clay to explain the November phenomena. It consists in 

 ; supposing that, independently of the great planets, there exist in the planetary 

 ( regions myriads of small bodies which circulate about the sun, generally in 

 ) groups of zones, and that some of these zones intersect the ecliptic, and are, 

 { consequently, encountered by the earth in its annual revolution. The princi- 

 ) pal difficulties attending this theory are the following : 



J First, that bodies moving in groups in the circumstances supposed, must 

 necessarily move in the same direction, and consequently they become visi- 

 ble from one point and move toward the opposite. Now although the observa- 

 tions seem to show that the predominating direction is from northeast to south- 

 west, yet shooting stars are observed on the same nights to emanate from all 

 points of the heavens, and to move in all possible directions. Secondly, their 

 average velocity (especially as determined by Wartmann), greatly exceeds that 

 which any body circulating about the sun can have at the distance of the earth. 

 Thirdly, from their appearance, and the luminous train which they generally 

 leave behind them, and which often remains visible for several seconds, some- 

 times for whole minutes, and also from their being situated within the earth's 



