THEORY OF THE EARTH. 23 



which the successive steps may be perfectly ascer- 

 tained, although the duration of their intervals 

 cannot be defined with precision. They are so 

 many fixed points, which serve to regulate and di- 

 rect our inquiries respecting this ancient chro- 

 nology. 



Examination of the Causes wJiich act at present on the 

 surface of the Globe. 



Let us now examine those changes which are 

 taking place at the present day upon the globe, in- 

 vestigating the causes which still act in its surface, 

 mid endeavouring to determine the possible extent 

 of their effects. This portion of the history of the 

 Earth is so much the more important, that it has 



greatest quantity, and at the greatest heights ; those of the 

 intervening spaces have not been carried so high. Among 

 the chains of the Jura mountains, which are more remote 

 from the Alps, they are only found in places which are op- 

 posite the openings of the nearer chains. 



From these facts, the author draws the conclusion, that 

 the transportation of these blocks has taken place at a period 

 subsequent to the deposition of the sandstones and conglo- 

 merates, and has perhaps been occasioned by the last of the 

 revolutions which the globe has experienced. He compares 

 the transportation in question to that which still takes place 

 from the agency of torrents ; but the objections presented by 

 the consideration of the great size of the blocks, and the deep 

 valleys over which they must have passed, appear to us to 

 militate greatly against this part of his hypothesis. Note E. 



