214 REACTION OF THE INTERIOR OF THE EARTH 



craters of elevation in basaltic districts ; and lastly, the 

 appearance of a permanent volcano within the crater of 

 elevation itself, or among the debris of its earlier formation. 

 At different epochs, and in different stages of activity and 

 force, permanent volcanoes em?*- aqueous or acid vapours 

 and ignited scoriae, or, when the resistance is overcome, 

 glowing streams of molten earth. 



Sometimes great but local manifestations of force in the 

 interior of our planet, acting by means of elastic vapours, 

 upheave portions of the Earth's crust in dome-shaped un- 

 broken masses of felspathic trachyte and of dolerite (Puy de 

 Dome and Chimborazo) ; or the upheaved strata are broken 

 through, so as to present a slope on the exterior side, and 

 a steep precipice towards the interior which forms the inclo- 

 sure or bounding wall of a crater of elevation. When it is 

 a part of the bottom of the sea which has been thus ele- 

 vated (which is by no means always the case), the form 

 and character of the upheaved island are determined there- 

 by. In this manner have originated the circular form of 

 Palma, so well described by Leopold von Buch, and also 

 that of Nisyros in the ^Egean Sea.( 211 ) Sometimes a part 

 of the annular circumference has been destroyed, and in the 

 bay where the sea has entered, families of coral animals 

 have built up their cellular habitations. Even on conti- 

 nents, craters of elevation are often filled with water, and 

 the lakes thus formed impart to the landscape a picturesque 

 beauty of a very peculiar kind. The formation of these 

 t craters of elevation'" is independent of the nature of the 

 rock ; they are found in basalt, trachyte, leucite porphyry 

 (Somma), and in combinations of augite and labradorite : 

 hence the varieties of their form and aspect. "No phenomena 

 of eruption, however, proceed from these craters; nor is 



