528 



On the age of Mountains. 



always imperceptible. On the contrary, we often observe 

 a sudden alteration in the nature and quality of the masses, 

 as well as in the strata themselves, and also in the remains 

 of organic beings imbedded in them. 



Thus for instance it is clear, that between the formation of 

 Jura limestone, and that of the green sand and chalk on 

 which it rests, an alteration in the state of things on the 

 earth's surface took place. The same can be said of that 

 epoch, which divides the chalk from the tertiary formation ; 

 it is likewise clear, that between the tertiary formation and 

 the formation of the early tertiary uplifted land, a decided 

 alteration must have taken place in the nature of the re- 

 mains, by which these mountain masses are distinguished. 



These great changes in the nature of those bodies deposit- 

 ed by the waters, are regarded by geologists as the effects of 

 those occurrences which they call the revolutions of the 

 earth, although it is difficult to say, in what these revo- 

 lutions have consisted ; yet it is nevertheless certain that 

 they have taken place. 



The order in which the formations succeed each other, 

 has been discovered by tracing uninterrupted, each moun- 

 tain mass to its connection with adjoining plains, in which 

 one can observe with certainty, on great horizontal ex- 

 tensions, that a certain formation lies on this, or that layer. 

 Mountain slopes, steep and high river banks, high coasts, 

 artesian and other wells, as also river channels, have in this 

 respect been of great service. 



with which a great quantity of small green grains occur, and is covered 

 with chalk strata. The coasts of France and England on the Channel, 

 present many cliffs which clearly shew this formation. Tertiary for- 

 mation consists of many layers of clay, lime, marl, gypsum and 

 sandstone. 



The early tertiary land (diluvium) and the Quaternary up washed 

 land, (alluvium) derive their names from their similarity to those aug- 

 mentations of sand, mud, &c, which are now daily formed by the 

 sea and the rivers. 



