62 



LYELL'S ELEMENTS OF GEOLOGY. 



Land has been raised, not the Sea lowered. 



unexplained those more common instances where strata are 

 inchned, curved, or placed on their edges, and evidently not in 

 the position in which they were first deposited. 



Geologists, therefore, were at last compelled to have recourse 

 to the other alternative, namely, the doctrine that the solid land 

 has been repeatedly moved upwards or downwards, so as per- 

 manently to change its position relatively to the sea. There are 

 several distinct grounds for preferring this conclusion. First, it 

 will account equally for the position of those elevated masses of 

 marine origin in which the stratification remains horizontal, and 

 for those in which the strata are disturbed, broken, inclined, or 

 vertical. Secondly, it is consistent with human experience that 

 land should rise gradually in some places and be depressed in 

 others. Such changes have actually occurred in our own days, 

 and are now in progress, being accompanied in some cases by 

 violent convulsions, while in others they proceed insensibly, or 

 are only ascertainable by the most careful scientific observations. 



On the other hand, there is no evidence from human experi- 

 ence of a lowering of the sea's level in any region, and the wa- 

 ters of the ocean cannot sink in one place without their level 

 being depressed every where throughout the globe. 



These preliminary remarks will prepare the reader to under- 

 stand the great theoretical interest attached to all facts connected 

 with the position of strata, whether horizontal or inclined, curved 

 or vertical. 



Now the first and most simple appearance is where strata of 

 marine origin occur above the level of the sea in horizontal posi- 

 tion. Such are the strata which we meet with in the south of Sicily, 

 filled with shells of the same species as now live in the Mediter- 

 ranean. Some of these rocks rise to the height of 2000 feet and 

 more above the sea. Other mountain masses might be men- 

 tioned with horizontal strata of high antiquity which contain fos- 

 sils wholly dissimilar in form to any now known to exist, as in 

 the south of Sweden, near Lake Wener, where the beds of a 

 deposit, called Transition or Silurian by geologists, occur in as 

 level a position as if they had recently formed part of the delta 

 of a great river, and been left dry on the retiring of the annual 

 floods. Aqueous rocks of about the same age extend, over the 

 lake-district of North America, exhibiting in like manner a strati- 

 fication nearly undisturbed. The Table Mountain at the Cape 

 of Good Hope is another example of highly elevated and per- 

 fectly horizontal strata, no less than 3500 feet in thickness, and 

 consisting of sandstone of very ancient data. 



Instead of imagining that such fossil iferous rocks were always 

 at their present level, and that the sea was once high enough to 



