964 HISTORICAL GEOLOGY. 



recessions ; and this was one means by which the moraine ridge was widened 

 and rendered irregular in height and surface. 



The foregoing figure of part of a moraine on Cape Ann, Mass., from a 

 paper by Shaler, though belonging to a later part of the Glacial history, shows 

 the common appearance of such moraines at the present time. 



A great feature of the epoch was the amount of water discharged, 

 making new channels by erosion and giving the streams in the region of 

 melting great transporting and eroding powers. The Delaware, Susque- 

 hanna, Ohio, and other streams were flooded ; and the Mississippi derived 

 waters not only from the Ohio with its many tributaries and from the icy 

 heights of the Rocky Mountains, but also through the Missouri from 

 British America, far north of Montana, perhaps from the upper portion of 

 the Saskatchewan. Distribution of the transported material supplied by 

 the melting ice, and erosion by the loaded waters went forward, therefore, 

 with unwonted energy. 



"With the continent at its high level, the flooded rivers over all the conti- 

 nent dug out their channels, during the time of maximum ice, often to great 

 depths ; then at the melting the channels were filled with till, and, over the 

 till, with fluvial beds of sand or gravel. The Mississippi valley received then 

 its earlier deposits of loess, over lake-like regions along its course, while 

 other portions of the valley had their coarser deposits. 



South of New England, the retreat was short. On Long Island, then probably 500 feet 

 high, the eroding waters carried olf seaward the terminal moraine of the south shore for 

 70 miles of its length, and dropped till over the denuded surface ; then later waters covered 

 it with sand and fine gravel ; for there are no bowlders or till to be seen over the even 

 slopes, although abundant elsewhere on the island. So also the waters that descended 

 the north slopes of the island from the moraine belt, cut out of the morainic accumulations 

 and underlying Cretaceous formation a number of short, steep valleys, and left them 

 similarly under fluvial sand-beds as the top-dressing, with no bowlders over their surface ; 

 and the valleys, after the Champlain subsidence — which restored the waters of the Sound 

 to their place — became the deep and capacious harbors of the north coast. 



Daring the epoch when the Mississippi was receiving waters, by the 

 Missouri, from the melting in progress through a thousand miles from 

 south to north, with other floods from the ice and snows to the east and 

 the glacier regions in the Rocky Mountains, the deposition took place, of 

 what has been named the Lafayette formation — the Orange sand formation 

 of Hilgard. As shown by Hilgard, the Lafayette was a widespread flood- 

 made formation, extending along the great valley of the continent, the 

 Mississippi, south of its junction with the Missouri, from southern Illinois to 

 the Gulf. Its eastern border passes near Cairo through western Kentucky 

 and Tennessee, and the northeast corner of the Mississippi, and, according 

 to L. Johnson, reaches the shore of Mobile Bay in Alabama. Its western 

 border crosses Arkansas and Louisiana into Texas. 



The formation is described as consisting mostly of rust-colored or reddish 

 siliceous sand-beds. Near the great river channels, notably that of the 



