leing projectedfrom the Moon. 1 13 



litigle of 9^ from the earth's place; this would amount to the 

 distance of an arc of36500milesand4i»=lS250,and2i° = 9125. 

 And this distance is far too great, and the obliquity of the line 

 of direction too much to admit of such projectile being attracted 

 to the earth, and falling on it. 



Beside this, it must be projected with a force which would 

 carry it 234,000 miles in about 8", to carry it to a point where 

 the attraction of the moon would no more than equal that of the 

 earth. This is a velocity of very near 30,000 miles in a second; 

 while that of the comet of 1680, for some few hours at its peri- 

 helion was only abont 800,000 miles an hour =8000 miles in 

 36"= 1000 in 4 1°. 



A body projected with such force would appear to have less 

 than a momentary duration, if it even passed us vertically from 

 east to west, allowing it to be much larger than any projectile 

 from the moon can be supposed to be. Its density and power 

 of cohesion must be inconceivablv great to prevent its being fused 

 and vanishing in vapour, or dispersed to atoms long before it 

 would reach the earth. And with such density, to what asto- 

 nishing depth must it not bury itself? And must not the force 

 and depth of such an explosion be sufficient to rend the moon 

 itself into fragments ? Nothing comparable happens in our vol- 

 canoes on earth. And supposing it projected even twenty dia- 

 meters of the moon from her, or 43,000 miles, when it had 

 reached that distance or long before ; the probability is, that it 

 would revolve round the moon as a sub-satellite. 



It costs little to make suppositions as to any phcenomena, till 

 the circumstances attending that supposition come to be ex- 

 amined. 



I agree with you, that it is infinitely more probable that they 

 should be found in our atmosphere, or perhaps in some rare in- 

 stances projected from mountains of our own. 



I remain, dear sir. Yours, &c. 



I;vs-,mh, Dec. 30, 1817- CapEL Lofft. 



The density of the moon according to Newton is as 21 to 17, 

 or as 7 to 5-J to that of the earth. This is so small an excess 

 that there is no reason for supposing a density of lunar much 

 superior to terrestrial projectile masses. Their very slow rotation 

 and her nearly equal sphericity may account considerably for 

 this very superiority of density. If it be supposed that a lunar 

 projectile mav be invisible on account of its sniallness till it has 

 approached near to the earth, the velocity which enables it to 

 overcome the moon's attraction must be vast indeed, and further 

 increased by its gravitation as it approached the earth, so that 

 nearly all the difficulties would remain. 

 I . Vol.51. No. 238, Feb. 1818. H The 



