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CHAPTER XVIII. 



ON EARTHQUAKES AND VOLCANOES. 



Phenomena that precede the Shock of an Earthquake.— Extent to which the Wa- 

 ters in Lakes and Springs are agitated during Earthquakes. — Extent to which 

 Earthquakes are felt on Land. — More severe in Mountains than in level Coun- 

 tries. — Connection between Earthquakes and Volcanoes. — Electrical Earth- 

 quakes. — First Appearance of a Volcano. — Common Phenomena attending 

 Volcanic Eruptions. — Remarkable Eruption of Sumbawa in 1815.— Long Peri- 

 ods of Repose in some Volcanoes. — Volcano of Popocateptl in Mexico. — Sub- 

 marine Volcanoes ; their Appearance preceded by violent Agitation of the Sea, 

 — Submarine Volcanoes in the Azores — in the Grecian Archipelago. — Recent 

 Submarine Volcano near Sicily. — Craters of Eruption. — Craters of Elevation. — 

 Theory of Von Buch confirmed by analogous Geological Facts. — Eruptions of 

 Mud and Water from Volcanoes.— Groups of Volcanic Islands. — Fall and Ex- 

 tinction of a Volcano. — Vast Extent of some ancient Volcanoes. — Extinct Vol- 

 canoes of Central France. — Puy de Pariou, the best preserved of ancient Volca- 

 noes. — Extinct Volcanoes in Germany and Asia. — Pseudo- Volcanoes. — Volca- 

 nic Rocks and Products. — Observations on Volcanic Fire. 



Accustomed to view the hills in our own country in a stale of 

 profound repose, presenting in each succeeding year, the same un- 

 varied outline, we can scarcely conceive the possibility of a whole 

 district being covered, in the space of a single night, with new moun- 

 tains and another soil ; yet, within the limits of authentic history, 

 such changes have been produced, by the united agency of earth- 

 quakes and volcanoes. For a particular description of recent vol- 

 canic eruptions, and the changes they have produced on the surround- 

 ing countries, I must refer the reader to the works of Spallanzani, 

 Dolomieu, Sir William Hamilton, and M. Humboldt, and to the re- 

 cent account of the Island of Java, by Lieutenant-Governor Raffles, 



In the present chapter I propose, 1st, to describe those phenome- 

 na that indicate the connection between earthquakes and volcanoes, 

 and between the volcanoes in distant countries ; 2dly, to take a view 

 of the most remarkable recent volcanic eruptions, and of the remains 

 of ancient volcanoes, that prove the extensive action of internal heat 

 on the crust of the globe ; and, 3dly, to give a concise account of 

 volcanic rocks and products. 



Earthquakes and volcanoes may be considered as different effects, 

 produced by the agency of subterranean fire. They frequently ac- 

 company each other ; and, in all instances, that have been observed, 

 the first eruption of a volcano is preceded by an earthquake of great- 

 er or less extent. Volcanoes do not make their appearance in every 

 country where the shock of an earthquake is felt : but earthquakes 

 are more frequent in volcanic districts than in any other. Earth- 

 quakes are, almost always, preceded by an uncommon agitation of 

 the waters of the ocean, and of lakes. Springs send forth torrents 



