596 



GEOGRAPHICAL BOUNDARIES 



[Ch. XXIII. 



great earthquakes. 



om 



of the 



Lisbon shock in 1755, that the first movement 



proceeded from the bed of the ocean ten or fifteen leagues 

 from the coast. So late as February 2, 1816, when Lisbon 

 was vehemently shaken, two ships felt a shock in the ocean 

 west from Lisbon; one of them at the distance of 120, 

 and the other 262 French leagues from the coast*— a fact 



moi 



Grecian Archipelago, the volcanic region of Southern Italy, 

 Sicily, Southern Spain, and Portugal, will, if prolonged west- 

 ward through the ocean, strike the volcanic group of the 



subm 



nection with the European line. 



In regard to the volcanic system of Southern Europe, it 

 ^ n^prtr^ tfia.t. there is a central tract where the 



may 



greatest earthquakes prevail, in which rocks are shattered, 



mountains 



laid in ruins. On each side of this line of greatest commo- 

 tion there are parallel bands of country where the shocks are 



less violent. 



Norther 



for example, extending to the foot of the Alps) , there are 

 spaces where the shocks are much rarer and more feeble, yet 

 possibly of sufficient force to cause, by continued repetition, 

 some appreciable alteration in the external form of the earth's 

 crust. 'Beyond these limits, again, all countries are liable to 

 slight tremors, at distant intervals of time, when some great 



mo"v 



canic region; but these may be considered as mere vibrations, 



mechanically 



the globe, 



almost 



distances 



through the air. Shocks of this kind have been felt in Eng- 

 land, Scotland, Northern France, and Germany— particularly 

 during the Lisbon earthquake. But these countries cannot, 

 on this account, be supposed to constitute parts of the south- 

 ern volcanic region, any more than the Shetland and Orkney 

 Islands can be considered as belonging to the Icelandic circle, 

 because the sands ejected from Hecla have been wafted 

 thither by the winds. 



* Verneur, Journal des Voyages, torn. iv. p. 111.— Von Hoff, vol. ii. p- 275. 





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