AND JFRE6H-WATER FORMATIONS. 331 



in antient times, fishes had only been migratory, as 

 they are at present, it is plain that the fossil remains 

 of those animals can never aid us in deciding on the 

 character of a stratum. That many of the fresh water 

 amphibia now frequent the sea, from choice, is known 

 respecting the alligators of Cumana, and those of the 

 Pellew and the Bahama islands. In a reverse way, the 

 Turtle of the West Indies has been taken alive in the 

 fresh water of the Tamar, whither it had wandered of 

 itself, after a residence of unknown length. That it 

 will also reside for a long time, and continue to thrive, 

 in fresh water, has been proved in Kent. 



If my own views as to this subject are now termi- 

 nated, I presume that I ought still to notice one of the 

 theories that has been entertained respecting it ; as it 

 might still possess an injurious weight if not thus ex- 

 amined, though the answers might easily be derived 

 from what has been said. They who speak of retreats 

 of the sea consequent on its diminution, are but offer- 

 ing that gratuitous and untenable hypothesis which so 

 long weighed down geology as to the older rocks. 

 As far as is necessary, these dreams will be examined 

 in a future place. Any other retreat would only ex- 

 plain the alluvial deposits already distinguished. I 

 shall sum up this chapter with a brief statement of 

 what I consider an arrangement for all the strata later 

 than the great marine series. 



If no general revolutions have occurred since the 

 great marine elevation, the facts of the last chapter prove 

 that there have been great partial ones, dependent on 

 volcanic actions. By these have aestuaries, marine 

 basins, and fresh water lakes, been elevated ; while 

 the volcanic matter needs not be present, since it is 

 not always so in the Coral islands. And these, being 



