METEORS OF AUGUST AND NOVEMBER. gi 



average discrepancies of less than one-third of that value. The first result is 

 such as we should naturally expect, since, in the case of bodies moving with 

 all varieties of directions and velocities, there must be a compensation of these 

 velocities resolved each at the time of visibility in the direction of the ob- 

 server's tangential motion. The second result — the smallness of the average 

 discrepancy — if it leads to any conclusion at all, shows that the average true 

 velocity of the meteors is small, or the mean discrepancy of the relative veloci- 

 ties would be greater. Lastly, this mean relative velocity of shooting stars is 

 so great as to preclude the possibility of a terrestrial or lunar origin. Since 

 it follows from the laws of gravity, according to the remark of Olbers,^" 

 Laplace,^' Hassler,^^ and others, that the mean relative velocity of a satellite 

 of the earth, at its nearest possible approach to the observer, is only about 4.29 

 geographical miles, and its maximum in a re-entering orbit only 6.06 geogra- 

 phical miles. Hence all bodies of our system which, when visible to us, have 

 a relative velocity beyond this limit, must be moving relatively to the earth in 

 a hyperbolic orbit, and must, in a few hours, leave the earth's sphere of acti- 

 vity, and again become, as they must have been before, cosmical bodies. The 

 grounds for the latter remark, that bodies having a relative velocity of 18.3 

 miles cannot have acquired the same by any force belonging to the atmo- 

 sphere, nor by any volcanic or other explosive force in the earth or moon, are 

 manifest. Indeed, the explosive force of gunpowder communicates a velocity 

 of only a fourth of a geographical mile per second," and a velocity of seventy 

 times that amount cannot be ascribed to any force known to exist in the earth or 

 moon; and certainly no such force must, on account of this observed relative 

 velocity alone, be presumed to exist, when other phenomena point to the sun's 

 central force as amply sufficient to furnish such a relative velocity as the re- 

 sultant of a cosmical body's true and the observer's known tangential motion. 



^0 Jahrbuch, for 1837, p. 56. Note. ** Systeme du Monde, L. iv. chap, v, 



="" Mem. Am. Phil. Soc. Vol. vi., P. II., Art. xv. 



^^ Monat. Corr. June 1812, p. 564. The velocity of a twenty-four pound cannon-ball is stated 

 by Lagrange at 1398 Paris feet per second. 



