EARTHQUAKE MEASUREMENT AT MIYAKO. 177 



probably still greater, but was unfortunately obscured by the 

 proper oscillations of the pendulum. The corresponding maxi- 

 mum vertical motion was 0.57 mm., its period being 0.6 second. 

 There existed in the (EW) still slower undulations of an 

 average period of 1.7 seconds, the maximum motion of this 

 kind being 2a=1.6mm., period = 1.8 seconds. 



18. Eqke. No. 14. The 7th August, 1897 ; 9.9.7 p. m. 

 Intensity, slight. The earthquake had its origin probably at 

 nearly the same locality as earthquake No. 13, the disturbed 

 area being, however, smaller in this case. 



The duration of the H.M. was 150 seconds, and that of 

 the V.M. was 60 seconds, the character of the motion being 

 gentle and indicative of a distant origin. 



The preliminary tremor, whose duration was 23 seconds, 

 consisted of fine ripples of an average period of 0.08 second 

 in the (EW), which were prominent only for the first 5.8 

 seconds, becoming thereafter very small. 



The principal portion, in which the motion was greater in 

 the (EW) than in the (NS), consisted of slow undulations of 

 an average period of 1.6 seconds in the (EW), 1.0 second in 

 the (NS), and 0.8 second in the (V), these^being in the earlier 

 portion of the epoch superposed upon by traces of ripples. 

 The maximum horizontal range of motion of slow undulations 

 was 2a=0.9 mm. toward NE, T = 1.0 second ; and the correspond- 

 ing maximum vertical motion was 2^=0.12 mm., T=0.78 second. 



19. Eqke. No. 15. The 16th August, 1897 ; 4.53.3 p. m. 

 Intensity, iveah. The origin of this earthquake was probably a 

 little nearer to the coast than that of the two preceding ones. 



The duration of the H.M. was about 140 seconds, and that 

 of the V.M. was 70 seconds, the character of motion being mild 



