MUSEUM OF COMPARATIVE ZOOLOGY. 155 



sixty miles in width, we see that in a relatively short time, by the action 

 of ocean waves alone, this amount of detritus has been moved. If the 

 conditions had been such that the Gulf Stream had co-operated with 

 the wave action, it is not improbable that we should have had a mass 

 equivalent to all (if the sands of the interior of Florida removed from 

 the ocean floor, and brought to near the level of high tide. 



If the surface of the lake district, and of Florida generally, was shaped 

 beneath ocean waters affected by strong currents, we are compelled 

 to believe that the elevation of the area above the sea level took place, 

 not in a gradual manner, but with extreme suddenness, at least for 

 all the height above the level of high tide. If the lake district had 

 emerged from the sea by a gradual upward movement, the ocean waves 

 would have produced a total change in the configuration of the surface ; 

 the incoherent sands of the hills would have been worn away, and moved 

 into the hollows. The aspect of the surface would be that of sand 

 beaches and plains extending towards the shores. If in the process of 

 elevation there had been pauses in the movement, during which the sea 

 even for a brief time, say for a few months, beat along a particular level, 

 then we should have had long beach lines with inclined aprons in their 

 fronts, such as now mark the elevated borders of our great lakes. So 

 far, I have not been able clearly to determine the existence of such fea- 

 tures in the Florida hilly country. At a few points indistinct signs of 

 such action are exhibited, but the wooded and swampy condition of the 

 country makes it difficult to trace these features. They will only be- 

 come apparent, if they exist at all, on careful study of the field. My 

 observations lead me to suppose that, if such features exist, they are 

 very imperfectly developed, and that, if we assume this surface to have 

 taken shape under water, we have likewise to assutne a tolerably rapid 

 elevation, which brought it above the level of the sea. 



The problem in this field is substantially like that which we have in 

 the kame districts along the southern shore of New England. I have 

 elsewhere endeavored to show that these forms were clearly formed 

 beneath the surface of the sea, and came above it by a movement so 

 speedy that in the case of Nantucket the most delicate heaps of sand 

 were not disturbed by the ocean surges. 



In the present state of my inquiries concerning the recent movements 

 on the eastern shore of North America, the evidence from the kame dis- 

 trict and that from the lake district of Florida appear alike to point to 

 the conclusion that a sudden elevation, or a series of such movements, 

 took place during the present geological period, a movement which must 



