96 Dynamic Theory. 



CHAPTER XIY. 



QUARTERNARY OR POST-TERTIARY PERIOD. 



This period is divided by American geologists into the (1) Glacial 

 Epoch, during which the Northern parts of America and Europe were 

 elevated one or two thousand feet, and the temperature so lowered as to 

 produce an accumulation of ice from the pole to latitude 40 North in 

 America, and to 50 in Europe. 



(2) The Champlain Epoch, in which there was a gradual depression 

 of the same regions until they were 500 to 1,000 feet lower than now, 

 bringing large tracts under the sea. 



(3) The Terrace Epoch, in which there was a series of slow elevations 

 interrupted by occasional pauses bringing geological history to the 

 present or recent times. 



The plants and marine shell animals of the Glacial Epoch are such as 

 now live in an arctic climate. They flourished along the southern edge of 

 the ice cap and emigrated North as that edge retreated at the closing of 

 the epoch. The same progress in Mammal development that was 

 noticed in the Tertiary period is continued into the Quartenary. The 

 advance southward of the cold would drive most of the species south 

 and modify all of them. On the return of a favorable climate, the 

 living representatives of the old tribes came back, and new ones with 

 them. All the species seem to be at their best, and the remains of 

 Mastodons, Elephants, Bisons, Horses, Stags, Beavers, are all called 

 " gigantic" of their kind. There were Tapirs, of course, and Pecca- 

 ries and Edentates from South America. There were two species of 

 Bear and one of the Lion. The climate during the Champlain Epoch, 

 in which the greater part of Mississippi valley was down almost to the 

 level of the sea and much of it submerged under the warm waters of 

 the Gulf, was very favorable to the support of very populous tribes. 

 But the gradual elevation of the continent during the Terrace times 

 brought unfavorabe conditions. In addition to this, I suspect that one 

 of the most unfavorable circumstances was the advent of MAN upon the 

 scene soon after the close of the Glacial Epoch. It is pretty certain he 

 came before the extinction of the great Mammals, an event to which he 

 certainly contributed. There is evidence of his presence both in Europe 

 and in this country, on the Pacific slope. Probably he came into the 

 Mississippi valley later, and it is probable that the great Mammals 

 were there to a comparatively late date. 



The European Quarternary has a history quite like the American. 



