CHAPTER IX. 

 SPECIAL GEOLOGY. 



Modern Geological Changes. 



BEFORE we enter on the history of the past, we shall direct 

 the student's attention to the present ; and previously to 

 describing the vicissitudes which the earth has undergone 

 during the remote epochs of its history, we purpose to 

 devote a few pages to the account of those changes which 

 have occurred in our own island within the historical period. 

 The sketch must be brief; for to enumerate the whole of 

 these would require a separate treatise. 



"Wherever we direct our observation, in the natural world, 

 we discover that a law of mutation is impressed on all created 

 objects, as one of the conditions of their existence. Every 

 operation of Nature affords examples of this law. Heat and 

 cold, moisture and drought, the warmth of summer and the 

 frost of winter, the snow and the ice, perform their part in 

 displacing and renewing the solid crust of the earth. The 

 agencies by which these changes are effected, may be divided 

 into destructive and conservative. 



The phenomena of Nature had early engaged the atten- 

 tion of philosophic observers, and Ovid's description com- 

 prises the chief agencies in operation at this moment ; 

 such as "the change of land to sea, and of sea to land ; the 

 excavation of valleys ; the destruction of hills, and the 

 transfer of their materials to the sea ; the transition of dry 

 ground to marshes* and the reverse; the occurrence of 

 earthquakes, and the phenomena they produce ; the union of 

 islands with mainlands, the insulation of peninsulas, and 

 those instances of change which characterise the varying 

 condition of the crust of our globe. The laws of Nature 



