b 



DISTEIBUTION OF EARTHQUAKES IN TIME. 249 



primary disturbances, they might have been treated in a 

 previous chapter. 



As examples of consequent or secondary earthquakes 

 Fuchs tells us that when small earthquakes take place in 

 Constantinople and Asia Minor, earthquakes are felt in 

 Bukharest, Gralazy, and Kronstadt. 



The great Lisbon earthquake also appears to have 

 given rise to several consequent disturbances. One was 

 in Derbyshire, occurring at 11 a.m. It was sufficiently 

 violent to cause plaster to fall from the sides of a room 

 and a cha'sm to open on the surface of the ground. Some 

 miners working underground were so alarmed that they 

 endeavoured to escape to the surface. During twenty 

 minutes there were three distinct disturbances. 



Another shock was felt at Cork.^ 



Although these disturbances own a consequence of the 

 Lisbon earthquake they might properly perhaps be at- 

 tributed to the pulsations produced by the shock at Lis- 

 bon, which spread through England and other countries 

 without being felt. 



The shocks which men felt in New Zealand and New 

 South Wales in 1868 were probably secondary shocks, 

 due to the disturbance at Arequipa and other places on 

 the South American coast. 



These so-called secondary earthquakes, although in 

 many instances they may be due to earth pulsations pro- 

 duced by earthquake, or to the immediate sensible shaking 

 of a large earthquake, may perhaps, in certain instances, 

 be attributed to some widespread disturbance beneath the 

 crust of the earth. The occurrence of periods where all 

 earthquake countries suffer, unusual disturbances iudicate 

 the probability of such underground phenomena. 



* Phil. Trans, vol. xlix. pt. i. 



