OUR CHIEF TIME-PIECE LOSING TIME. 41 



differential equations involved in the problem of the 

 lunar motions that is, when the eccentricity is made 

 a function of the time non-periodic or secular terms 

 appear in the expression for the moon's mean motion ' 

 and so on ? Let it suffice to say that Laplace had 

 considered only the work of the sun in diminishing 

 the earth's pull on the moon, supposing that the slow 

 variation in the sun's direct influence on the moon's 

 motion in her orbit must be self-compensatory in long 

 intervals of time. Adams has shown, on the contrary, 

 that when this variation is closely examined, no such 

 compensation is found to take place; and that the effect 

 of this want of compensation is to diminish by more 

 than one-half the effects due to the slow variation 

 examined by Laplace. 



These views gave rise at first to considerable 

 controversy. Pontecoulant characterised Adams's pro- 

 cesses as * analytical conjuring-tricks,' and Leverrier 

 stood up gallantly in defence of Laplace. The contest 

 swayed hither and thither for a while, but gradually 

 the press of new arrivals on Adams's side began to 

 prevail. One by one his antagonists gave way ; new 

 processes have confirmed his results, figure for figure ; 

 and no doubt now exists, in the mind of any astronomer 

 competent to judge, of the correctness of Adams's views. 



But, side by side with this inquiry, another had 

 been in progress. A crowd of diligent labourers had 

 been searching with close and rigid scrutiny into the 

 circumstances attending ancient eclipses. A new light 

 had been thrown upon this subject by the labours of 



