OUR CHIEF TIMEPIECE LOSING TIME. 59 



factorily for solar and hmar eclipses, makes the moon's 

 rate of motion increase more than twice as fast as it 

 should do according to the calculations of Adams. 

 But before our readers run away with the notion that 

 astronomers have here gone quite astray, it will be 

 well to present, in a simple manner, the extreme 

 minuteness of the discrepancy about which all the coil 

 has been made. 



Suppose that, just in front of our moon, a false moon 

 exactly equal to ours in size and appearance (see note 

 at the end of this paper) were to set oft' with a motion 

 corresponding to the present motion of the moon, save 

 only in one respect namely, that the false moon's 

 motion should not be subject to Ihe change we are 

 considering, termed the acceleration. Then one hun- 

 dred years would elapse before our moon would fairly 

 begin to show in advance. She would, in that time, 

 have brought only one-one-huudred-and-fiftieth part 

 of her breadth from behind the false moon. At the 

 end of another century, she would have gained four 

 times as much ; at the end of a third, nine times as 

 much : and so on. She would not fairly have cleared 

 her own breadth in less than twelve hundred years. 

 But the whole of this gain, minute as it is, is not left 

 unaccounted for by our modern astronomical theories. 

 Half the gain is explained, the other half remains to 

 be interpreted ; in other words, the moon travels far- 

 ther by about half her own breadth in twelve cen- 



