Natural History of Volcanos and Earthquakes. 273 
produce a mountain, whilst the latter remain at the height to 
which they are borne up by the elastic fluids. 
~ In elevations of the latter description, the vapor cannot escape 
through the uplifted mass. This mass is supported by the elas- 
tic foree of the vapor, cools gradually, and then remains, as it 
Were, wedged in between the strata it has broken through. But 
according to Von Buch’s* observations on Palma and Gran Ca- 
narta, it may happen, that the vapor bursts forth from the centre 
of the mass it has raised, and thus exposes its interior. Sucha 
crater would thus be the effect of the elevation of the island, 
for which reason he gives it the name of crater of elevation, 
(Erhebungs Krater,) to distinguish it from the craters of erup- — 
tion, by which true volcanos open a communication with the at- 
mosphere. 
Further, this philosopher has pointed ont,t+ that voleanie cones 
cannot be generated by the building up of streams of lava. He 
infers this from observations made by Elie de Beaumont, and 
Which have been already alluded to. This philosopher meas- 
uted the mean inclination of about thirty lava streams of E’tna, 
and of a great many of Vesuvius, aud found that a stream hav- 
Mg an inclination of 6°, or even more, forms no continuous 
mass. Such a stream inclines too much 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.t 
astly, 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 conse- 
ence of the elevations, were observed before,$ and during]} the 
famous earthquake of Lisbon. Small elevations also took place 
uring that in Calabria. The commissioners who were em- 
Ployed to make observations of the earthquakes in the county of 
ignerol, relate, that the very day (2d April, 1808) when one 
WiGigge ll ats 
&e. 
ol. xx. p. 376, &c. Edin. New Phil. 
Journ. * and Description Geologique de la France, t- iv. 
§ Palassou Mém. pour. servir & !' Histoire Nat. des Pyren. p. 260. 
I) Philos. Trans. t. xlix. p. 417. q Jour. de Phys. Ixii, 1806. p. 264. 
Vol. Axxv1, No, 2.—April-July, 1839. 30 
