

TREMORS OVER THE SURFACE OF AN ELASTIC SOLID. 



23 



The function has a maximum value + '67643 when#/ = 1 '01368 ; it changes sign 



when 0/a = T22474 ; and it has a minimum value '159319 when 9ja = 1'62076.* 



The graph of this function is shown in the upper part of fig. 4. If the scales be 



Fig. 4. 



properly chosen, the curve will represent the variation of M O with t, during the 

 " preliminary" disturbance, at any assigned point x. For this purpose the horizontal 

 scale must vary directly, and the vertical scale inversely, as x. 



* The calculations were made almost entirely by Mr. H. J. WOODALL, to whom I am much indebted. 



