242 REACTION OF THE INTERIOR OF THE EARTH 



habited by crocodiles, called the Laguna de Bombon. 

 The cone, which was ascended in Kotzebue's voyage 

 of discovery, has a crater lake, out of which again rises 

 a cone of eruption with a second crater. ( 337 ) This 

 description recalls involuntarily the mention, in the 

 journal of Hanno's voyage, of an island enclosing a 

 small lake, in the middle of which a second island rises. 

 Two such instances would seem to have been met with, 

 one occurring in the Grulf of the Western Horn, and 

 the other in the Bay of the Gorilla Apes on the west 

 coast of Africa. ( 338 ) Descriptions so particular would 

 tend to make one believe them based on actual observa- 

 tion of nature I 



The least and the greatest height of points at which 

 the volcanic activity of the interior of the earth mani- 

 fests itself permanently at the surface, is a hypsometric 

 consideration interesting to physical geography, to 

 which belong all facts relating to the reaction of the 

 fluid interior of the planet against its surface. The 

 measure of the upheaving force ( 339 ) is, indeed, mani- 

 fested in the height of volcanic cones ; but great caution 

 is necessary before pronouncing any judgment as to the 

 influence of relative height upon the frequency and 

 strength of eruptions. Particular contrasts between 

 very high and very low volcanoes, in frequency and 

 strength of effects, can determine nothing ; and of the 

 several hundred active volcanoes supposed to exist on 

 continents and islands, our knowledge is still so incom- 

 plete, that the only decisive method, that of mean 

 values, cannot yet be regarded as applicable ; and, even 

 if such mean numbers could give us a definite result by 

 assigning the approximate altitude at which eruptions 



