THE PALMS OF THE ANCIENT WORLD, 173 . 



tions. Most rocks may be traced to one of two 

 origins — either tliey have been consolidated 

 from a liquid state, in which they had been 

 maintained by intense heat, or they hare been 

 gradually accumulated by the action of water, 

 wearing down more ancient rocks and lands, 

 and depositing the sediment in the deeper 

 portions of those primitive seas, or at the 

 bottom of the rivers and lakes. The larger 

 portion of the dry land on the surface of our 

 earth is covered with rocks and strata of this 

 character, and in this way sand, mud, and 

 other materials, are at this day accumulating at 

 the bottom of every sea and lake, and at the 

 outlet of every river. 



The land and sea have likewise undergone 

 very repeated and extensive changes of relative 

 level, land having sunk beneath the level of the 

 sea, and the bed of the sea having been elevated 

 and become dry land. It is easy to understand 

 how, in the lapse of time, where a portion of 

 the earth's surface has been thus repeatedly 

 submerged and laid dry again, it should have 

 become covered with several series of deposits 

 or distinct strata. As a single example, we 

 may cite the cliff at Lulworth Cove, in Dorset- 

 shire, which exposes on its face a section of 

 several strata, exhibiting to the eye the most 



