I06 PHILOSOPHICAL TRANSACTIONS. [aNNO 1714. 



that its perpendicular altitude was at least 38 miles: that in all places near this 

 course, it was heard to make a hissing noise as it passed, like that of artificial fire- 



of credibility to the whole narrative, and throw additional weight on the inference before drawn from 

 internal evidence, that tlie solitary masses of native iron found in different quarters of the globe, have 

 the same origin with the stones analysed by Howard and Vauquelin. 



Having now given a summary of the facts and evidence, as well witli regard to the circumstances 

 attending these singular bodies, as tlie ingredients they arc composed of, and their outward appearance 

 and structvu-e, we are now to consider what inferences respecting their probable origin, may be drawn 

 from this mass of information. And indeed we may safely conclude, as it has been inferred from the 

 whole, by the philosophers best qualified to judge of the circumstances, as follow, viz. that the 

 bodies in question have fallen on the surface of the earth j but that they were not projected by any 

 terrestrial volcanoes; and that we have no right, from the known laws of nature, to suppose that 

 they were formed in the upper regions of the atmosphere. Such a negative conclusion has been 

 thought all that we are, in the present state of our knowledge, entitled to draw. 



In this embarrasing predicament, the total want of any other possible way of accounting for the 

 origin of those bodies, an idea has been started, perhaps at first merely at random, that since there is 

 no other possible manner of accounting for them, then they must have dropped from the moon. And 

 indeed, this singular thought has now advanced into a serious hypothesis, which it must be allowed is 

 unmcumbered with any of the foregoing difficulties : having at least possibility in its favour, which 

 no other hypothesis yet proposed can claim. 



As the attraction of gravitation extends through the whole planetary system, a body, placed at the 

 surface of the moon, is affected chiefly by two forces, one drawing it toward the centre of the earth, 

 and another drawing it toward that of the moon. The latter of these forces however, near the 

 moon's surface, is incomparably the greater. But as we recede from the moon, and approach toward 

 the earth, this force decreases, while the other augments j till at length a point of station is found 

 between the two planets, where these forces are exactly equal ; so that a body, placed there, must 

 remain at rest ; but if it be removed still nearer to the earth, then this planet would have the superior 

 attraction, and the body must fall towards it. If a body then be projected from the moon towards 

 the earth, with a force sufficient to carry it beyond this point of equal attraction, it must necessarily 

 fall on the earth. Such then is the idea of the manner in which the bodies must be made to pass 

 from the moon to the earth, if that can be done, the possibiUty of which is now necessary to be 

 considered. 



Now supposing a mass to be projected from the moon, in a direct line towards the earth, by a 

 volcano, or by the production of steam by subterranean heat ; and supposing for the present those two 

 planets to remain at rest ; then it has been demonstated, on tlie Newtonian 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 tlie moon's mass is now allowed 

 to be much 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 pro- 

 jecting a body with a velocity of less than a mile and a half per second. But we have known cannon 

 balls projected by the force of gunpowder, with a velocity of 2500 feet per second, or upwards, that 

 is, about half a mile. It follows therefore, that a projectile force, communicating a velocity about 

 three times that of a cannon ball, would be sufficient to throw the body from the moon beyond the 

 point of equal attraction, and cause it to reach the earth. Now tliere can be little doubt that a force 

 equal to that is exerted by volcanoes on the earth, as well as by the production of steam from sub- 

 terranean heat, when we consider the huge masses of rock, so many times larger than cannon balls. 



