NIAGARA FALLS AND VICINITY 1 29 



a long period of time remained above the sea. During this time, 

 the Helderbergian and other Lower Devonic strata were deposited 

 In the Appalachian region, which by that time had established a 

 southern connection with the open Atlantic. 



Finally, toward the middle of the Devonic era, the sea once more 

 transgressed on the abandoned continent, and again all this region 

 was covered by oceanic waters. On the land surface of early Devonic 

 times, now grew corals in great luxuriance; and reefs of great ex- 

 tent, with their accompanying deposits of coral sands, and their 

 wealth of new life, again characterized the interior Paleozoic sea. It 

 was not till long ages after, that this portion of the continent was 

 again raised above the sea. This last elevation, which took place 

 toward the close of Paleozoic time, was a permanent one, with the ex- 

 ception of a possible slight resubmergence of some parts of this region 

 after the close of the glacial period. With the last great emergence 

 of the land were inaugurated those long cycles of erosion outlined 

 in chapter i, which resulted in the formation of the great topo- 

 graphic features of this region, and which came to a close only with 

 the envelopment of this region in the snow and ice of the great 

 glacial winter. 



