PLEISTOCENE SUBMERGENCE ON THE ATLANTIC COAST. 409 



Professor N. S. Shaler : I should like to ask whether this evidence, 

 brought to us from north of the boundary to the United States, does not go 

 still further and show that the last glacial period in North America was in 

 some way connected with the conditions of the northern Atlantic ocean ? 

 The evidence now goes to show that it is a symptom of climatic conditions 

 on the north Atlantic ; and therefore it is our task to interpret the phe- 

 nomena by the facts that have taken place in that ocean basin. It seems to 

 me it is by the increased precipitation of the vapors taken from the warm 

 waters to the sea that we may most easily explain the conditions of the last 

 ice period. 



I have recently had an opportunity to study the surface geology of Florida, 

 and it seems to me probable that in the glacial times, or about the time of 

 the last glacial period, the Gulf Stream flowed freely over the surface of 

 Florida up to the northern portion of the lake district. The appearance 

 of Florida seems to indicate that the tide at this time extended from the 

 northern part of the lake district to the Cuban shore. It seems to me likely 

 that we may attribute a glaciation in the eastern part of Europe and Asia 

 and the northern part of North America to the changes in the flow of this 

 stream dependent on modifications of the coast line topography of the region 

 of the Caribbean and the Gulf of Mexico. 



Mr. W J McGee: I have recently ascertained that during early Pleisto- 

 cene time — during the first of the two great ice invasions which all geologists 

 are recognizing — not only was all of Florida submerged, but two-thirds of 

 Georgia and the greater part of South Carolina. The submergence in South 

 Carolina reached 550 or 600 feet, and over the low-lying plains there lies a 

 mantle of coast sands deposited during the period of submergence. These 

 coast sands have been found continuous Avith the Columbia formation of 

 the northern part of the Atlantic slope. 



Dr. J. W. Spencer : With the conclusions of Professor Shaler and Mr. 

 McGee I concur. I have seen apparent Pleistocene deposits in Alabama at 

 about 675 feet above the sea. Over plains and hills of the great Northwest 

 of Canada, also, I have seen bowlders scattered upon the surface of both 

 Paleozoic and Cretaceous rocks. In many cases these are of secondary origin, 

 having been left upon the washing away of the finer materials from the older 

 bowlder clay. Few or none of those erratics which I have seen have been 

 primarily derived from their original sources, although many have been 

 again transported by the floating ice of now shrunken or extinct lakes or 

 seas. 



From the occurrence of elevated beaches described by Mr. Tyrrell and 

 others in the North West territories, and from the remains of still higher 

 beaches about the Great Lakes, I am inclined to generalize and bring down 

 the whole continent to make the beaches mark sea-level in the last stages of 

 the Pleistocene period after the episode of the last till. 



