1881.] Notes on the Earthquakes of July, 1880, at Manila. 467 



" We will now recapitulate briefly what we understand by the 

 figures. 



" On the 14th, which is that represented in fig. 1, we notice two- 

 foci of seismic radiation, the first situated in the second quadrant, 

 where it began, and the second situated in the first quadrant, where 

 it terminated. In the earthquakes of the 18th we also discover the 

 same two foci; but two others also appear which impelled the pen- 

 dulum in every imaginable direction, as may be seen in fig. 2. 



"Proceeding to that of 3 p.m. on the 20th, we find that the focus of 

 the second quadrant acted with astounding violence, and the others 

 disappeared (fig. 3). We turn now to fig. 4, which represents to us 

 the violent repetition of 10 p.m. on the 20th, and we observe a great 

 variation with regard to the foci of seismic radiation. In it we see 

 that the oscillations from east to west, and which correspond to the 

 focus, which before had acted with so much violence, were gradual 

 and of much less intensity. On the contrary, that from north-east to 

 south-west showed a great degree of undulation from these points. 



Fig. 5. 



"Finally, in fig. ~No. 5, which represents the last important oscil- 

 lation on the morning of the 25th, we only note the focus of seismic 

 radiation of the first quadrant operating with very little intensity, the 

 other foci having entirely disappeared. We do not care at present 

 to form deductions from the above observations, we have preferred 

 to present them to general notice in order that scientific persons might 

 form their own conclusions without being biassed by our opinions. 



" Note 1st. Observe, that in speaking of the swing of seismic un- 

 dulation from both sides of the centre of reference (place of instru- 

 ment), we do not mean to say that the buildings moved from one side 

 to the other like the pendulum, because it is very clear that the latter 

 was only moved in one of the semi-undulations by the effect of the 



