On Stones which have fallen from the Heavens. 29 1 



fill back to the earth, but would continue to move from it 

 in infinitum. A cannon bullet fometiines acquires a velocity 

 of 1800 or 2000 feet in a fecond*; and heavy niaflTes are 

 projedted from the volcanoes of our earth with a velocity, 

 four or five times as great. This velocity, therefore, is far- 

 greater than that of 35,000 feet per fecond. But even if it 

 were poflible, by the help of chemiilry and mechanics, to 

 give a ball a velocity of -35,000 feet, or even more, per fe- 

 cond, the ftrong .refiftance oppofed by the air, which always 

 increafes at the lea ft as the fquare of the vehicity, would tend 

 verv much to deftrov it. We may therefore confider it as 

 alnioft impoffible that heavy bodi.es can ever be entirely pro- 

 jedted from the earth. I confider it altogether unneceflarv 

 to take into account in this calculation the influence which 

 the attradive force of the moon would have on the motion 

 of a body proje6led in this manner. ;;' ", ■ ' '"■ 



But the cafe is entirely different if we^fubjedl to calcula-^ 

 tion the motion of a heavy body projefted from the furface 

 of the moon. The moon is a great deal fmailier than the 

 earth, poflTefl'es a much weaker power of attra£lion, and at 

 the fame time its atmofphere is of fo fmall extent, and fo 

 rare, that it could oppofe very little refiftance to a heavy, 

 body in a (late of motion. It is therefore poffible that a 

 heavy body mitiht be projected from the moon with fuch a 

 velocity as to carryit to a diftance where it would be altradled 

 vcith greater force by the earth. 



It is found bv calculation that 7780 feet per fecond is the 

 minimum of velocity with which a body projeiled frojn the 

 moon would require to fall upon the earth. It appears, there- 

 fore, that if heavy bodies were projefted from the moon with 

 a vertical velocity of 7800 or 8000 feet under certain circum- 

 ftances, fome of thel'e bodies would reach the earth and fall 

 down upon it. Such a velocity appears to me to be very 

 poffible. The furfaceof the moon, by the new craters which 

 arife, (hows evident traces of violent eruptions, by which 

 even as great or greater velocity might be communiciated to 

 the bfxlies thrown up by thent. ,. , i, . • 



It appears then, that it is notaltogether impofliblelhat the 

 ftoiies or mades which have been feen^lo fdl fron) the hia- 

 vcn.s, and which, though entirely different from all the-mi- 

 neral bodies of our earth, have a great refeniljlance to each 

 other, may have fallen from the moon.- 'It is ih their great 

 fimilarity and corrofpondence that the grounds of ihis-opiuion 

 are to be found; for the fnnilarity.of "their external appear- 



' Mem. dc I'Acad.RoyMp des Stienccs :jL^, p. 147. 



U a ance. 



