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On the Natural History of Volcanos and Earthquakes. By Dr 

 GusTAv BiscHOF, Professor of Chemistry in the University 

 of Bonn. Communicated by the Author. (Concluded from 

 page 81.) 



Earthquakes. 



EARTHauAKEs, SO closely connected with volcanic phenome- 

 na, are undoubtedly owing to the same causes. That the pro- 

 cesses by which they are produced must take place at a great 

 depth is evident from the simultaneous occurrence of earth- 

 quakes at places far distant from one another. Some extraor- 

 dinary examples in this respect are furnished by the memorable 

 earthquake at Lisbon, on the 1st November 1755, which was 

 not only felt over a great part of Europe., but extended to the 

 northern coast oi Africa and the Antilles ; and farther, by the si- 

 multaneous shocks felt on the 16th November 1827, at Ochotsk 

 and Bogota, which places are 1900 geographical miles distant 

 from each other, and are separated both by land and sea.* 

 Parrotf has calculated that about 700,000 German miles, that 

 is, nearly one-twelfth of the whole surface of the earth, was 

 shaken by the earthquake at Lisbon. Stukeley | calculated 

 from the extent of country over which earthquakes have been 

 felt, that the force must, in some instances, be 200 English 

 miles beneath the surface. But Daubeny§ pointed out that we 

 must not lay any stress on his remarks, because we have reason 

 to believe that the vibrations may be propagated laterally far 



* Von Humboldt's Reise. &c. vol. i. p. 497, and vol. iii. p. 23 and 27. 

 Yon HoiF, Verzeiclmiss Von Erdbeben, &c. in Poggendorflf 's Ann. vol. xxi. 

 p. 214. 



t Physik der Erde, p. 289. See also Berghaus' Almanack, 1837, p. 106, 

 on the great extent of this extraordinary earthquake. With respect to 

 this, it is worthy of remark, that Vesudusj winch was in some excitement on 

 the morning of the 1st November 1755, became suddenly quiet at the very 

 hour of the shock ; and that, as Von lloff relates, the column of steam 

 which rose, returned into the crater. The same happened during the 

 earthquake in Cakihria. The little volcano of Stromboli, which is continually 

 active, subsided, and almost ceased smoking. 



t On the causes of earthquakes, Philos. Trans, for 1750. 



§ Loco cit. p. 388. 



