7 IN STARRY REALMS. 



from a balloon which has ascended two or three miles into 

 the air will duly fall to the earth. A meteorite, which i& 

 often a lump of solid iron, may tumble down here from an 

 altitude of unknown miles. The tendency to fall to the 

 earth certainly exists at a height of ten miles, or fifty 

 miles, or hundreds ot thousands of miles. Why, then,, 

 does not the moon fall ? There is assuredly no material 

 structure to keep it up, no scaffolding to enable the moon 

 to resist the earth's attraction; why, then, does it not 

 tumble down ? We feel pretty confident that it is not 

 falling down, for the moon is not nearer to the earth now 

 than it was a twelvemonth ago ; for hundreds of years, or 

 thousands of years, our satellite has approached no nearer 

 to the earth. In fact, we have already seen that in so far 

 as there is any difference at all, the moon is getting 

 farther away from us instead of coining nearer. Nor can 

 we suppose that at the great distance of the moon, the 

 tendency to fall earthwards ceases to operate. No doubt 

 our satellite is a quarter of a million miles away, but 

 it is not that circumstance which preserves its position. 

 If a stone or a world or anything else were taken up a 

 quarter of a million of miles and simply let go, it would 

 unquestionably tumble down on the earth. In the fall of 

 a body from the height of the moon to the earth, it would 

 move very slowly at first ; so slowly indeed that the 

 movement performed in the first minute would not exceed 

 that fallen in fhe first second, where the body was let 

 drop near the earth. As the journey proceeded, the pace 

 would gradually mend, would gradually become rapid and 

 ever increasing ; the body would at last crash down on the 

 earth, after a journey lasting altogether about five days. 



