172 



EAETHQUAKES ON THE PACIFIC COAST 



movement in minute waves was 0.9 second of arc, and the period 

 of the pulsations about three seconds of time and not regular, at 

 times almost subsiding and then starting out afresh. The move- 

 ment was apparently from the south. This continued for four or 

 five minutes, and in six minutes the amplitude of the waves was 



Fig. 



of the seismograph in San Francisco. (Magnified.) 



from 0.2 or 0.3 second of arc, and the time of pulsation slower. 

 The pulsation was faintly exhibited for nine minutes and in thir- 

 teen minutes it had ceased. At the close the north ends of the 

 two levels were 0.5 second of arc higher than when first read. 

 Prof. Davidson says that this w^as one of those earthquakes that 



