EARTHQUAKE SHOCKS AND OTHER CONCUSSIONS. 225 



C is proceeding in space with this velocity, and under the action of a force </> s, 

 always tending to the point A (now stationary). 



In this second stage 



T=- 4>s as before; 



At the moment that s S, -^ became = -^, because x ceasing to increase, y hence- 

 forth = s. 



rf? 

 Hence, by (9) when s = S, - - = V {1 - cos <y< . T)} = U . . . . (10). 



''' 



(ii) 



''' 4 



But =-(> + , or /= 



-v/U'+^S 2 -^ 



'--L -~~ 1 . ^ -iv 



When * = T , * = S 



(12). 



- -r v T - *r ~ j 



i i 



Let sin" 



The greatest () value of s is when V (* - T) + = 90, 270 & c . ; and it is then 



+ 



It recurs regularly () as ,/ ^> t increases by TT, or as 



*7r 

 # hicreases by r (15). 



v/ <p 



By (14) and (10) 



- cos (V (ft . ))+ S j 



