Natural History of Volcanos and Earthquakes. 41 



Art. lY. — On the Natural History of Volcanos and Earth- 

 quakes f by Dr. Gustav Bischof, Professor of Chemistry in 

 the University of Bonn. Communicated by the Author. Con- 

 cluded from Vol. xxxvi, No, 2, page 283. 



EARTHQUAKES. 



Earthq,uakes, 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 of Africa and the Ajtfilles ; and farther, by the si- 

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

 and Bogota^ which places are 1900 geographical miles distant 

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

 ParrotJ 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 Daubenyjt pointed out that we must 

 not lay any stress on his remarks, because we have reason to be- 

 lieve that the vibrations may be propagated latterly far beyond 

 the immediate influence of the impelling force. In a former 



* From the Edinburgli New Philosophical Jour., Vol. xxvi, No. 52, April 1830. 

 t Von Humboldt's Reise, &C., va). i, p 497, and vol. lii, p. 23 and 27. Von 

 Hoff, Verzeichniss Von Erdbeben, &c- in Poggendorff's Ann. vol. xxi, p. 214. 



I Physik der Erde, p. 289. See also Berghau?' Ahnanack, 1S37, p. liJ6, on the 

 great extent of this extraordinary earthquake. With respect to this, it is worthy 

 of remark, that Vesuvius^ which 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 Iloff relates, the column of steam which rose, returned into the crater. 

 The same happened during the earlliquake in Calabria, The little volcano of 

 StTomboli, which is continually active, subsided, and ahno:*! ceased smoking. 



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



Jl Loco cit, p. 3tf8. 



Vol. xxwii, No. 1.— July, 18^, bis. , 6 



