EARTHaUAKES. 215 



on tlie Lelantine plains near Chalcis * The intelligent geog 

 rapher of Amasea, to whom we are indebted for the notice of 

 this circumstance, further remarks : " Since the craters of ^tna 

 have been opened, which yield a passage to the escape of fire, 

 and since burning masses and water have been ejected, the coun- 

 try near the sea-shore has not been so much shaken as at the 

 time previous to the separation of Sicily from Lower Italy, when 

 all communications with the external surface were closed." 



We thus recognize in earthquakes the existence of a vol- 

 canic force, which, although every where manifested, and as 

 generally diffused as the internal heat of our planet, attains 

 but rarely, and then only at separate points, sufficient intensity 

 to exhibit the phenomenon of eruptions. The formation of 

 veins, that is to say, the filling up of fissures with crystalline 

 masses bursting forth from the interior (as basalt, melaphyre, 

 and greenstone), gradually disturbs the free intercommunica- 

 tion of elastic vapors. This tension acts in three difierent 

 ways, either in causing disruptions, or sudden and retroversed 

 elevations, or, finally, as was first observed in a great part of 

 Sweden, in producing changes in the relative level of the sea 

 and land, which, although continuous, are only appreciable at 

 intervals of long period. 



Before we leave the important phenomena which we have 

 considered, not so much in their individual characteristics as 

 in their general physical and geognostical relations, I would 

 advert to the deep and peculiar impression left on the mind by 

 the first earthquake which we experience, even where it is not 

 attended by any subterranean noise.t This impression is not, 



* Strabo, lib. i., p. 100, Casaub. That the expression tztjIov ScaTci)- 

 pov TTora/jtov does not mean erupted mud, but lava, is obvious from a 

 passage in Strabo, lib. vi., p. 412. Compare Walter, in his Abnakme der 

 Vulkanischen ThdtigkeU in Historischen Zeiten (On the Decrease of Vol- 

 canic Activity during Historical Times), 1844, s. 25. 



t [Dr. Tschudi, in his interesting work. Travels in Peru, translated 

 from the German by Thomasina Ross, p. 170, 1847, describes striking- 

 ly the effect of an earthquake upon the native and upon the stranger. 

 ** No familiarity with the phenomenon can blunt this feeling. The in- 

 habitant of Lima, who from childhood has frequently witnessed these 

 convulsions of nature, is roused from his sleep by the shock, and rushes 

 from his apartment with the cry of Miaericordia ! The foreigner from 

 the north of Europe, who knows nothing of earthquakes but by descrip 

 tion, waits with impatience to feel the movement of the earth, and longs 

 <,o hear with his own ear the subterranean sounds which he has hitherto 

 considered fabulous. With levity he treats the apprehension of a com- 

 ing convulsion, and laughs at the fears of the natives ; but, as soon as his 

 wish is gratified, he is terror-stricken, and is involuntarily prompted to 

 seek safety in flight."] — Tr. 



