350 ON VOLCANOES AND EARTHQUAKES. 



more distant origin, explanatory of the still anterior 

 revolutions of the Earth. 



As might be expected, few subjects have produced 

 more writers. But we search in vain through the 

 great mass of their works, for useful or scientific in- 

 formation. Even the scientific investigators, anxious 

 to maintain some favourite theory, and educated in 

 prejudices respecting tftose rocks in nature which hear 

 the greatest analogy to volcanic products, have rarely 

 done justice to a subject, of which the principal ob- 

 scurity will probably be found to arise from their own 

 peculiar views. 



Of the Geography of Volcanoes. 



However numerous the existing volcanoes may be, 

 their extent and numbers have once been far more 

 considerable ; as is proved by the extinct remains 

 found in many parts of the world. The great age of 

 some of those has been inferred from their rocks 

 being, in some places, covered by strata of secondary 

 limestone. But the nature of this fact has been mis- 

 taken ; as these strata have been formed beneath the 

 sea, and elevated by the volcanic power. It is the 

 very case described in the last chapter. Such vol- 

 canic rocks are therefore not necessarily older than 

 the traps, because they are beneath the strata while 

 the latter are above them. On the contrary, the re- 

 verse may be inferred ; as time has carried away 

 those strata which have unquestionably covered the 

 trap rocks in many places, while those which thus 

 lie on the volcanic products, remain. If geology 

 could be proved to have reasoned worse on one sub- 

 ject than another, it has been on this one. There 

 are doubtless many differences of age among extinct 



