EFFECTS OF THE ALTERNATIONS. 199 



and a section of the plain would doubtless show 

 many alternations of marine, brackish, and fresh- 

 water strata, similar to those upon which we have 

 been speculating. Small as may be the area, and 

 limited as the time under consideration, they are 

 not unworthy of our earnest inquiry. The history 

 of life upon our globe, the in-coming of new spe- 

 cies, and the perishing of old ones, is only the 

 history of elevations, depressions, and tem- 

 porary conditions, varied by an occasional convul- 

 sion, differing only in degree from those which 

 have determined the zoo-geological features of 

 the coast of Lycia. 



When describing the fresh-water tertiaries of 

 the valley of the Xanthus, we referred to similar 

 tertiaries in the island of Cos. These were 

 visited by us, on our voyage from Rhodes to 

 rejoin the Beacon, after leaving Lycia. They 

 present phenomena of striking interest and im- 

 portance, and as they bear on the question of 

 the possibility of a transmutation of species, we 

 cannot do better than append a notice of them to 

 this account of the geology of Lycia. 



The fresh-water tertiaries of Cos are of con- 

 siderable extent. They appear to belong to the 



