218 REPORT— 1898. 



2 . 43 . 29 r.M. 



11 . 40 . 48 A.M. 



No. 140.— Potsdam. 



No. 141.— Shide, Oct. 20, 1897. 



^4ii»i 



No. 141. — Potsdam, 

 8.54.21 P.M. 



No. loC— Shide, Dec. 28, 1807. 

 8.24.39 p.m. 



No. 15C.— Toronto. 



No. 157.— Shide, Dec. 20, 1S07. 

 11 . 32 . 20 A.M. 



No. 157. — Toronto. 



V. On Certain Characteristics of Earthquake Motion. 



1. The Character of Earth Waves near to their Orirjin. 



From the feelings of those who reside in earthquake districts, and 

 more definitely from seismograms, we have learned that the movements 

 of the ground constituting an earthquake of moderate intensity, which 

 in an epifocal area may shake badly constructed chimneys and loosen 

 tiles upon a roof, as observed at distances of approximately 20 or 100 

 miles from its origin, consist of preliminary vibrations, a shock or shocks 

 separated by more or less irregular waves, and a series of concluding 

 vibrations. At distances of from 100 to 200 or 300 miles the pre- 

 liminary vibrations may not be felt, or even recorded, on an ordinary 

 seismograph, and instead of a shock or shocks we obtain a record of 

 a series of long-period but irregularly recurring waves. These movements 



