Elevation and Depression of Land. 1 1 



maintain the average balance of sea and continent, 

 the amount of land elevated must exceed that de- 

 pressed, or be equal to the amount of that depressed by 

 gradual submergence, added to that destroyed by de- 

 gradation. 



The evidences of past elevation and depression are 

 simple. 1st. A large proportion of the rocks in many 

 mountain ranges, however high above the sea, contain 

 marine fossils, generally of extinct species. Such strata 

 are in great part highly disturbed, broken, contorted, 

 often pierced by igneous intrusions, and largely denuded. 

 2nd. On all continents and on many large islands raised 

 beaches occur, and also superficial accumulations of 

 loose strata, lying on the older rocks, and yielding shells, 

 in great part, or altogether identical with those that 

 now inhabit neighbouring seas ; and these organic re- 

 mains occur in such a manner, that it is plain they 

 lived and died on the spots where they lie, ere those 

 parts of the sea-bottom were elevated. In Britain, 

 such beds are found more than 1,000 feet above the sea ; 

 and in South America, 1,300 feet on the western side 

 of the Andes. 3rd. Experience shows that certain 

 volcanic regions subject to earthquakes are often areas 

 of elevation. The earthquake of 1835 in Chili is an 

 instance when a large tract of the coast of South America 

 was suddenly raised from four to twelve feet, and part 

 of the sea-bottom converted into land ; and it is prob- 

 able that similar causes have conduced to raise by 

 degrees the shelly strata above alluded to, to the height 

 of 1,300 feet above the level of the sea. The chain 

 of the Andes is volcanic, and the elevating forces and 

 earthquakes of South- Western America are connected 

 with this circumstance. The Mediterranean volcanic 

 region (though marked by many oscillatory movements) 



