248 EARTHQUAKES. 



when the town Euphemia sank, and in the years 1770, 

 1776, 1780, and 1783. 



A remarkable example of coincidence occurred on 

 November 16, 1827, when a terrible earthquake was felt 

 in Columbia, and at the same time a shock occurred on 

 the Ochotsk plains, nearly antipodal to each other. 



Kluge also gives a large number of instances of 

 simultaneous earthquakes; thus, on January 23, 1855, on 

 the same day that Wellington, New Zealand, so severely 

 suffered, there was a heavy earthquake in the Sieben- 

 geberge, and also in North America. To this might be 

 added the fact that the last destructive earthquake in 

 Japan occurred within a few days of this time. 



Sometimes neighbouring countries where earthquakes 

 are common are equally remarkable by their utter want 

 of synchronism. For example. Southern Italy and Syria 

 are said never to be shaken simultaneously. 



Secondary earthquakes, — Although it is possible that 

 the simultaneous occurrence of earthquakes in distant 

 regions may sometimes be a matter of chance, it must 

 also be remarked that the shaking produced by one earth- 

 quake may be sufficient to cause ground which is in a 

 critical state to give way, and thus the first disturbance 

 becomes the originator of a second earthquake. Admit- 

 ting that an earthquake, as it radiates from its centre, 

 may act in such a manner, we see that a feeble disturb- 

 ance might be the ultimate cause in the production of 

 a destructive earthquake, just as the disturbance of a 

 stone upon the face of a scarp might, by its impact 

 upon other stones, cause many tons of material to be 

 dislodged. 



It is also easy to conceive how the seismic activity of 

 two districts may be dependent upon each other. Inas- 

 much as these secondary shocks are direct effects of 



