a et 
eae oe SS 
Natural History of Volcanos and Earthquakes. Al 
Arr. IV.—On the Natural History of Voleanos and Earth- 
quakes ;* by Dr. Gustav Biscuor, Professor of Chemistry in 
the University of Bonn. Communicated by the Author. Con- 
cluded from Vol. xxxvi, No. 2, page 282. 
EARTH QUAKES. 
EartuQuakes, 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 Ist November 1755, which was 
not only felt over a great part of Europe, but extended to the 
northern coast of Africa and the Antilles ; 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.t 
Parrott 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 be- 
lieve that the vibrations may be propagated latterly far beyond 
the immediate influence of the impelling force. In a former 
* From the Edinburgh New Philosophical Jour., Vol. XXvi, No. 52, April 1839. 
t Von Humboldt’s Reise, &c., vol. i, p. 497, and vol. iii, p. 23 and 27, Von 
Hoff, Verzeichniss Von Erdbeben, &c. in Poggendorff’s Ann. vol. xxi, p. 214. 
t Physik der Erde, p. 289. See also Berghaus’ Almanack, 1837, p. 106, on the 
|| Loco eit. p- 388. 
Vol. xxxvir, No. 1.—July, 1839, bis. 6 
