EARTHQUAKES. 171 



others already lost, have broken out with earth-shocks. A 

 similar thermic connection is indicated in the remarkable 

 book of Johannes Lydus upon earthquakes (De Ostentis, cap. 

 liv., p. 189, Hase). The great natural phenomenon of the 

 destruction of Helice and Bura, in Achaia (373 B.C. ; Cos- 

 mos, vol. iv., p. 188), gave rise in an especial manner to hy- 

 potheses regarding the causal connection of volcanic activ- 

 ity. With Aristotle originated the curious theory of the 

 force of the winds collecting in the cavities of the depths of 

 the earth (Meteor., ii.. p. 368). By the part which they 

 have taken in the early destruction of the monuments of the 

 most flourishing period of the arts, the unhappy frequency 

 of earthquakes in Greece and Southern Italy has exercised 

 the most pernicious influence upon all the studies which have 

 been directed to the evolution of the Greek and Roman civ- 

 ilization at various epochs. Egyptian monuments also, for 

 example that of a colossal Memnon (27 years B.C.), have 

 suffered from earthquakes, which, as Letronne has proved, 

 have been by no means so rare as was supposed in the val- 

 ley of the Nile (Les Statues Vocales de Memnon, 1833, p. 

 23-27, 255). 



The physical changes here referred to, as induced by earth- 

 quakes by the production of fissures, render it the more re- 

 markable that so many warm mineral springs retain their 

 composition and temperature unchanged for centuries, and 

 therefore must flow from fissures which appear to have un- 

 dergone no alteration either vertically or laterally. The 

 establishment of communications with higher strata would 

 have produced a diminution, and that with lower ones an 

 increase of heat. 



When the great eruption of the volcano of Conseguina (in 

 Nicaragua) took place, on the 23d of January, 1835, the 

 subterranean noise* (los ruidos subterraneos) was heard at the 

 same time on the island of Jamaica and on the plateau of 

 Bogota, 8740 feet above the sea, at a greater distance than 

 from Algiers to London. I have also elsewhere observed, 

 that in the eruptions of the volcano on the island of Saint 

 Vincent, on the 30th of April, 1812, at two o'clock in the 

 morning, a noise like the report of cannons was heard with- 

 out any sensible concussion of the earth over a space of 

 160,000 geographical square miles.f It is very remarkable 



* Acosta, Viajes cientificos a los Andes ecuator iaies, 1849, p. 56. 

 f Cosmos, vol. i., p. 208-210 ; Humboldt, Relation Historique, t. iv., 

 chap. 14, p. 31-38. Some sagacious theoretical observations by Mai- 



