RIVER TERRACES AND GLACIAL SERIES 453 



yet recognized here, but an intermediate stage, probably equiva- 

 lent to the maximum extension of the Brown's Gulch glacier. 



GENERAL CONCLUSIONS. 



The preceding detailed descriptions seem to have pretty 

 definitely developed the following: 



1. That there was apparently a very old glaciation which 

 connects chronologically with the highest series of river terraces 

 developed in the Pleistocene valleys between Summerville and 

 the coast. 



2. That there was an intermediate stage of glaciation which 

 connects definitely with one of the intermediate terraces down 

 the river. 



3. That there was a last great glacial stage which connects 

 indefinitely with the lowest series of river terraces, including 

 the " flat valley floor " of the basins between Summerville and 

 the coast. 



The relation between the glacial deposits and the river terraces 

 is of extreme importance because a knowledge of it enables us 

 to roughly determine the relative ages of the different glacial 

 stages by erosion studies in a region without the glaciated area 

 and where conditions were more uniform. In this manner I 

 derive the following ideas: 



1. That the intermediate glacial stage (always referring to 

 the maximum extension of the ice in each glacial stage) was 

 about three times as long ago as the last glacial stage. 



2. That the earliest apparent glacial stage occurred at least 

 ten times and perhaps twenty-five times as long ago as the last 

 stage. 



Now, in personally inspecting the various drift sheets in the 

 Mississippi basin and in comparing my observations with those 

 of others, I have acquired the idea that the lowan drift is from 

 three to five times as old as the Wisconsin, the Illinoian ten or 

 fifteen times as old as the Wisconsin, and the Kansan at least 

 fifty times as old as the Wisconsin. Hence, there naturally 

 follow, as final conclusions : 



I. That the deposits of the last great glacial stage in the 

 Klamath mountains fully represent the Wisconsin glaciation. 



