ITi On the Origin of Stones 



random, that since there is no other possible manner ai 

 accounung for them, then they must have dropped from 

 the moon. Ar.d, indeed, this singular thought has now 

 advanced into a serious hypothesis, which it must be 

 allowed is unincumbered with any or the foregoing difficul- 

 tiesj having :.t least possibility in its favour, which no other 

 hypothesis vet proposed can claim. 



'" As the attraction of gravitalinn extends through the 

 whole planctarv system, a body placed at the surface of the 

 moon is aflected chiefly by two forces, one drawing it 

 toward the centre of the earth, and another drawing it to- 

 ward that of the moon. The latter of these forces how- 

 ever, near the moon's surface, is incomparably the greater. 

 But as we recede from the moon, ar.d approach toward the 

 earth, this force decreases, while the other augments, till 

 at length a point of station is found between the two 

 planets, where the^e forces are exactly equal ; so that a body 

 placed there must ven)ain at rest : but if it be removed still 

 nearer to tlie earth, then this planet would have the superior 

 attraction, and the body must fall towards it. If a body 

 then be projected from the njoon towards the earth, with 5 

 force sufficient to carry it beyond this point of equal attrac- 

 tion, it must necessarily fall on the earth. Such then is 

 the idea of the manner in which the bodies nmst be made 

 to pass from ih.e moon to tlie earth, if that can be done, 

 \.\\& possihUity of which is now necessary to be considered. 



'< Now supposing amass to be projected from the moon, 

 in a direct Imc towards the earth, by a volcano, or by the 

 production of steam by subterranean heat, and supjiosing 

 for the present those two placets to remain at rest, then it 

 has been demonstrated, on the Nev/tonian estimation of 

 the moon's mass, that a force projecting the body with a 

 velocity of 1 2,000 feet in a second, would be sufficient to 

 carry it beyond the point of equal attraction. But this 

 estimate of the moon's mass is now allowed to be nmch 

 above the truth ; and on M. Laplace's calculation it appears 

 that a force of little more than half the above power would 

 be sufficient to produce the effect, that is, a force capable of 

 projcctinc; a bodv Vv ith a vclocitv of less than a mile and a 

 half per second. But we have known cannon balls pro- 

 jectetl by the force of gunpowder, Vv-ith a velocity of 2500 

 feft per second, or, upwards, that is, about half a mile. It 

 follows therefore, that a projectile force, communicating a 

 velocityaboutthreetim.es that of a cannon ball, would be 

 suOicie'nt to throw the body from the moon beyond the 

 P'.nnt of equal attractiouj and cause it tu reach the earth. 



Now 



