S3XKOUS CAM KS OF CHANGE, 235 



CHAPTER V ,. 



Volcanic Erupt! us. 



" Yon dreary plain, forlorn and wild, 

 The seat of tie ;olation, void of light, 

 Save what the glimmering of these flames 

 Casts pale a d dreadful." Milton. 



WE have in the preceding chapters given somewhat in detail 

 an account of the various aqueous causes of change, now in ope- 

 ration. We sh? II consider in the present chapter the igneous 

 causes of chang , or volcanic action ; and in order to economise 

 the little space v e can allow, will consider them as follows. First, 

 we shall give a sketch of the geographical distribution of the 

 chief volcanoe now active, or which have been active within the 

 historic era. We shall next give an account of the principal 

 earthquakes, nd other volanic phenomena which have disturbed 

 the earth's so .-face; and lastly, consider such changes, supposed 

 to be due to internal igneous agency, as the gradual elevation and 

 depression of various tracts of country. It would be out of place 

 for us to discuss at present, the question, whether the interior of 

 the globe is in a state of fusion, and that the eruptive force of 

 volcanoes is the occasional liberation of the molten mass, acted 

 upon by the intense pressure of the superincumbent strata, or by 

 confined gases and vaj ors ; or whether th intense heat which 

 melts masses of rock, causing the most violent convulsions, is 

 caused by chemical action, i. e. the union of oxygen derived 

 from water or the air, with the metallic bases of the earths and 

 alkalies, forming silica, alumina, lime, soda, &c., substances 

 which predominata in lavas; or whether it be a union of both 

 these causes. In our own opinion it is neither, but is the result 



