i881.] Notes on the Earthquakes of July, 1880, at Manila. 463 



from the 5th to the 14th no notices of earthquakes in any part of the 

 island were received in Manila. 



"On the 14th, at 12 h. 33m. p.m., being threatened with a storm 

 from the north-east, indicated by an extraordinary fall of the baro- 

 meter, we experienced here the first shock, in which we observed that 

 two centres of oscillation were combined (see fig. No. 1), one on the 

 second quadrant, from whence the pendulum of the horizontal seismo- 



Fig. 1. 



meter began to oscillate ; and the other from the third, where the 

 oscillation of this first movement terminated, and which was chiefly 

 horizontal ; the amplitude of total oscillation reached 5° 25'. The 

 horizontal pendulum inscribed a cross with arms almost at right angles, 

 the first bearing from S.E. 10° E. to N.W. 10° W. ; the second from 

 S.W. 5° W. to KE. 5° E. 



" The first impulse was in the direction from south-east to north-west. 

 The amplitude of this oscillation described an arc of 5° 25', and 

 appeared to be formed by the first shock, because the pendulum 

 almost at once oscillated in a direction almost perpendicular to the 

 first. The amplitude of this second oscillation was somewhat less than 

 that from the first impulse. 



" The index of the vertical seismometer departed 4 millims. from its 

 position. After this first movement, we experienced two more shocks 

 in the space of an hour and a-half ; on the 15th and 16tk there were 

 no perceptible movements ; on the 17th, two slight shocks were felt. 



" It was on the 18th, at 12 h. 40 m. p.m., when the great earthquake 

 of oscillation, trepidation, and what is commonly called rotatory move- 

 ment, occurred simultaneously. Its duration was 1 m. 10 s. 



"It is impossible to describe all the movements of the pendulum on 

 account of their number and variety. We shall therefore confine our- 



