15G 



MR. R. D. OLPIIAM OX THE PROPAC. \TIOX OF 



their great sensitiveness to minute tilts, do not seem so well adapted for picking up 

 and recording the wave motion represented by the first and second phases. To what- 

 ever cause this may be due, the records printed above show that, with regard to these 

 phases, they do not respond with the same constancy or concordance as the heavy 

 weighted pendula favoured in the Italian observatories. 



Taking the records of the first phase motion, and separating the records of the 

 heavy pendula with mechanical record from the light photographic pendula, we get the 

 following results : 



First Phase ; heavy pendula. 



Here there will be noticed a close accordance in the time intervals and the apparent 

 rate of transmission, both of them increasing as the distance from the origin increases, 

 but not in the same ratio. The only break of any significance in the regular increase 

 is in the case of earthquake No. 4, and even this becomes unimportant when it is 

 remembered that the uncertainty of the exact time and place of origin, combined 

 with the shortness of the interval, may produce an error in the calculated rate of time 

 amounting to nearly 1 kilom. per second. 



The photographic records show a greater irregularity, but the general result is the 

 same, as may be seen from the following tabular statement : 



First Phase ; light pendula. 



