l6 CONNECTICUT GEOL. AND NAT. HISTORY SURVEY [Bull. 



There is need of a large amount of new study before the true 

 history of the glacial and aqueo-glacial formations of the state 

 can be determined. 



Dr. F. P. Gulliver of Norwich has been at work for some 

 time on a detailed study of the terraces bordering the estuary 

 of the Thame's. These shelves of stratified sand and gravel at 

 a considerable elevation above the present level of the river have 

 been supposed to be remnants of a great plain of sand and gravel 

 which was once substantially continuous across the valley, and 

 which was formed, after the retreat of the ice from the portion 

 of the valley in question, by deposition in the waters of the 

 river, whose velocity was at that time feeble by reason of dimin- 

 ished slope and excessive load of sediment. A number of years 

 ago Dr. Gulliver published a preliminary paper on the terraces 

 of the Thames, in which he gave reasons for the belief that those 

 terraces were formed on the edges of the valley while a tongue 

 of ice still lingered in the central part. Various students have 

 shown reasons for a similar belief as regards the terraces in the 

 lower or estuarine portions of other rivers of the North Atlantic 

 slope. The study of these terraces is therefore of great interest 

 in the endeavor to trace out the detailed history of the later 

 stages of the ice age. Dr. Gulliver has accordingly undertaken 

 to make a more detailed survey of the terraces of the Thames 

 River, and to furnish the result for publication as a bulletin 

 of the State Survey. 



Numerous other problems present themselves in the detailed 

 study of the glacial geology of this region. Studies of the 

 glacial formations in the Mississippi Valley, in northern Europe, 

 and in the Alpine region, have clearly revealed the fact that the 

 Glacial period was more complex than was formerly supposed. 

 There were repeated alternations of rigor and mildness in the cli- 

 mate in accordance with which the great ice sheets alternately ad- 

 vanced and retreated. The deposits of earlier ice sheets can be 

 recognized in some regions, emerging from beneath the edge of 

 the later deposits, while in some localities stratified and fossilifer- 

 ous interglacial deposits can be recognized between the older and 

 the younger glacial formations. In New England the latest ad- 

 vance of the ice sheet extended beyond the shore line, and it has 

 been generally supposed that the latest ice invasion so thoroughly 



