EARTHQUAKE MOTION DEDUCED PROM EXPERIMENT. 65 



wave, at any station, is shorter than with a slow burning 

 explosive. 



Results obtained in Japan. — From some experiments 

 made by the author in the grounds of the Meteorological 

 Department in Tokio, the following results were obtained: — 







Velocity in 



Velocity in 



Velocity in 



Number of 



No. of 





feet per second 



feet per second 



feet per second 



Cartridges 



Explosion 





for tlie firit 



for the second 



for 400 ft. 



of Dynamite 







200 ft. (A to B) 



200 ft. (B to C) 



(A to C) 



(6 = 1 lb.) 





I. 



464 



186 



26.5 



8-3 



Vertical 



III. 



— 



211 



— . 



101 



vibrations 



IV. 



.352 



284 



281 



7-1 





V. 



343 



232 



277 



6-0 



Normal j 

 vibrations 1 



VI. 











407 



100 



VIL 







— 



616 



12-5 



Transverse | . 

 vibrations i 



VIII. 



— 



— 



344 



12-5 



The general results to be deduced from the above 

 appear to be : — 



1. For vertical motion. 



{a) For the first 200 feet. The velocity depends 

 upon the initial force — the greater the charge of 

 dynamite the greater the velocity. 



(6) For the second 200 feet. The above law only 

 appears in experiments IV. and V., but it must be 

 remembered that the origins of I. and III. were 

 farther removed from A than IV. and V. 

 The speed of the wave during the second 200 feet is 

 always less than during the first 200 feet. 



2. For normal vibrations. 



Here the speed between A and c is all that was 

 measured, but we again see that the greater 

 the initial force, or the nearer we are to the origin 

 of the disturbance, the greater is the velocity. 

 This velocity is greater than the velocity of the 

 vertical or transverse vibrations. 



