180 COSMOS. 



Concussions of the earth and sudden eruptions of fire 

 from volcanoes which have been long in repose, whether 

 these merely emit cinders, or, like intermittent springs, 

 pour forth fused, fluid earths in streams of lava, have cer- 

 tainly a single, common causal connexion in the high 

 temperature of the interior of our planet ; but one of these 

 phenomena is usually manifested quite independently of the 

 other. Thus, in the chain of the Andes in its linear exten- 

 sion, violent earthquakes shake districts in which unextin 

 guished, often indeed active, volcanoes exist, without the lat- 

 ter being perceptibly excited. During the great catastrophe 

 of Riobamba, the volcanoes of Tungurahua and Cotopaxi, the 

 former in the immediate \icinity, and the latter rather fur- 

 ther off, remained perfectly quiet. On the other hand, vol- 

 canoes have presented violent and long-continued eruptions, 

 without any earthquake being perceived in their vicinity, 

 either previously or simultaneously. In fact, the most de- 

 structive earthquakes recorded in history, and which have 

 passed through many thousand square miles, if we may judge 

 from what is observable at the surface, stand in no connexion 

 with the activity of volcanoes. These have lately been called 

 Plutonic, in opposition to the true Volcanic earthquakes, 

 which are usually limited to smaller districts. In respect of 

 the more general views of vulcanicity, this nomenclature is, 

 however, inadmissible. By far the greater part of the earth- 

 quakes upon our planet must be called Plutonic. 



That which is capable of exciting earth-shocks, is every- 

 where under our feet ; and the consideration that nearly 

 |ths of the earth's surface are covered by the sea (with 

 the exception of some scattered islands) and without any 

 permanent communication between the interior and the 

 atmosphere, that is to say, without active volcanoes, contra- 

 dicts the erroneous, but widely disseminated belief that all 

 earthquakes are to be ascribed to the eruption of some dis- 

 tant volcano. Earthquakes on continents are certainly propa- 



garded as standing under the dominion of Neptune, and Bet in opposi- 

 tion to the Saturnian continents. According to Herodotus (lib. ii, 

 c. 43 et 50), Neptune was a Libyan deity, and unknown in Egypt. 

 Upon these circumstances the disappearance of the Libyan lake 

 Tritonis by earthquake and the idea of the great rarity of earthquakes 

 in the valley of the Nile, see my Examen Critique de la Geograjjlue, t. i, 

 pp. 171 and 172. 



