72 Prof. Bischof on the Natural Historij of ^ 



He infers this from observations made by Elie de Beaumont, 

 and which have been already alluded to. This philosopher mea- 

 sured the mean inclination of about thirty lava-streams of Etna, 

 and of a great many of Vesuvius, and found that a stream 

 having an inclination of 6°, or even more, forms no continuous 

 mass. Such a stream inclines too mucli to be able to attain 

 more than a thickness of a few feet. When its inclination is 

 only 3° or less, the mass may be spread, and accumulated to 

 a considerable height* 



Lastly, we have to notice the upraisings which are the conse- 

 quences of earthquakes, and often extend to large islands and 

 whole tracts of country. Elevations of small compass, accom- 

 panied by partial depression, which is no doubt merely a con- 

 sequence of the elevations, were observed before,f and duringf 

 the famous earthquake of Lisbon. Small elevations also took 

 place during that in Calabria §. The commissioners who were 

 employed to make observations of the earthquakes in the county 

 of Pignerol, relate, that the very day (2d April 1808), when 

 one of the most violent shocks was felt, the masting engine at 

 Toulon was elevated more than an inch.|| This observation is 

 worthy of note, as it shews that many effects of earthquakes 

 may often take place at great distances from their seat, which, 

 owing to their minuteness, may escape observation, unless ca- 

 sually discovered. For accounts of elevations of a more con- 

 siderable kind in equatorial countries we are indebted to Hum- 

 boldt. The elevations in the island of Lancerote,^ and those 

 on the coast of Ciimana'^''^ are of this kind. 



The most remarkable instance of the elevation of great tracts 

 of country of late years, is that which took place in Chili, on 

 the 19th November 1822. For the account of this important 

 phenomenon we are indebted to Mrs Maria Graham, a well in- 



* Vide Memoir of Elie de Beaumont, in vol. xx. p. 376, &c. Edin. New 

 Phil. Journ. ; and Description Geologique de la France, t. iv. 

 t Palassou Mt^m. pour servir k ITIistoire Nat. des Pyren. p. 260. 

 X Pliilos, Trans, t. xlix. p. 417. § Jour, de Phys. Ixii. 1806. p. 264. 



II Idem, t. Ixvii. 1808. p. 308. ^I Relat. Hist. t. i. p. 188. 



** Ibid. t. ii. p. 279. 



