336 GEOLOGICAL FORMATIONS. 



find rocks which have resulted by deposition from 

 water. These masses, having been exposed to the action 

 of the heat below, have been considerably changed in 

 their character, and hence they are often called meta- 

 morphic ; but metamorphic rocks may, however, be of 

 any age. The rocks formerly termed the transition 

 series from their forming the connecting link between 

 the earlier formations are now, from the circumstance 

 of their being fossiliferous, classed under the general 

 term of palaeozoic rocks, to distinguish them from the 

 rocks in which no organic remains have been found. 

 Above these are found the secondary strata, and, still 

 more recently produced, we have a class now usually 

 denominated the tertiary formations. " Eternal as the 

 hills" is a poetic expression, implying a long duration ; 

 but these must, from the nature of things, eventually 

 pass away. The period of time necessary for the dis- 

 integration of a granite hill is vastly beyond the powers 

 of computation, according to our conception of the 

 ordinary bounds of finite things. But a consideration 

 of the results of a few years, under the influence of 

 the atmosphere and the rains, as shown in quantity of 

 solid matter carried off by the rivers, and deposited at 

 their mouths, will tend to carry conviction to every 

 mind, that a degrading process is for ever in action on 

 the surface of the earth. The earth itself may be 

 eternal, but the surface is continually undergoing mu- 

 tation, from various causes, many of which we must 

 briefly consider.* 



In regarding geological phenomena, the absence of 



* Geological Researches j by Sir Heniy De la Beche, C.B. 

 (Degradation of Mountains, p. 167.) Geological Manual, p. 184. 

 Principles of Geology ; by Sir Charles Lyell, 7th Edition, p. 

 150, 080. On the Denudation of South Wales, and the adjacent 

 countries of England; by Professor Andrew Ramsay; Memoirs 

 of the Geological Survey and Museum of Practical Geology, 

 vol. i. p. 297. 



