CONTRASTED WITH OTHER FORCES. 67 



The volcano casts forth its scorching showers of scoriae and 

 ashes, his pastures and vineyards are utterly consumed, and 

 his homesteads and villages like Pompeii and Herculaneum 

 are buried, so that for centuries their very places are un- 

 known. Or the red river of lava spreads slowly and irre- 

 sistibly down the mountain-side, crushing and consuming 

 the forest-growth like stubble, damming and diverting river- 

 courses, engulfing villas and towns, and converting the 

 fair face of nature into a wilderness of blistery slag and 

 "the blackness of desolation." 



Opposed to these terrific agencies, man stands utterly 

 impotent ; and alas for his ideas of this Scheme of Crea- 

 tion, if he cannot learn to associate them with its necessary 

 order and mechanism ! Exposed to incessant powers of 

 waste and degradation from without, the earth's crust is 

 only maintained in habitable equilibrium and variety of 

 surface by this power of vulcanism acting as incessantly 

 from within. As it now manifests itself by the three or 

 four hundred orifices known to geographers, so in all time 

 past have its manifestations been equally apparent now in 

 this region, now in that, now feebly, now with greater in- 

 tensity, fitful to all appearance, but obeying, we may rest 

 assured, some fixed and determinable law, could we only 

 grasp the multifarious conditions associated with its expres- 

 sion. As at present, so during all the geological periods, 

 we find that it has been gradually elaborating hills and 

 mountain-ranges, upheaving and consolidating the sediments 

 of the sea-bottom, giving diversity of surface to areas of 

 flat and uniform deposit, raising substances of utility from 

 inaccessible to accessible depths in the earth's crust, and 

 reticulating that stony fabric with lines and walls of injected 

 matter, which under the names of " dykes" and "faults" 

 restrain the percolation of its internal waters, and bring 

 them to the surface in thousands of living and refreshing 



