840 



[THE WONDERS OF GEOLOGY. ct. VIII. 



were engulfed in the erupted mineral masses at the bottom 

 of the sea ; and when this ocean-bed shall be elevated above 

 the waters, and explored by some Agassiz of future times, the 

 then fossil fish of the Mediterranean, imbedded in volcanic 

 tuff, will afford interesting subjects for the contemplation of 

 the geologist and the philosopher. 



20. Summary of Volcanic phenomena. — I have in- 

 dulged in these long extracts, because the vivid pictures 

 which they present of volcanic action, cannot fail to produce 

 a powerful impression on the mind, and cause it to revert 

 to the principles enunciated in the first Lecture, which sug- 

 gest the probability that the earliest condition of the earth, 

 and of the worlds around us, may have been that of vapour or 

 fluidity (ante, p. 48). Here we see the most solid and durable 

 materials of the globe reduced to a liquid state — seas of molten 

 rocks, with their waves and billows, their surge and spray, 

 giving birth to torrents and rivers, which, when cooled, 

 become the hardest and most indestructible mineral masses 

 on the surface of our planet ! 



The constant escape of aeriform fluids from volcanic 

 vents — the irresistible force which such elastic vapours 

 exert when pent up and compressed — an effect with which 

 our steam-boats and locomotive engines have made every 

 one familiar ; and the immense production of such gaseous 

 elements which must be taking place in the interior of the 

 globe, from the igneous action which is going on unremit- 

 tingly, afford a satisfactory explanation of the nature and 

 cause of earthquakes, and of those elevatory movements by 

 which the foundations of the deep are broken up, and raised 

 into chains of mountains, thousands of feet above the level 

 of the sea. The volcanic vents are, in fact the safety- 

 valves from which the caloric and gaseous fluids from the 

 interior of the earth escape into the atmosphere ; when these 

 channels become choked up, the confined gases occasion 

 earthquakes, dislocations of the rocks and strata, and eleva- 



