290 GEOLOGICAL EXCURSION TO THE HOCKY MOUNTAINS. 



nndiained. The more elongate hills of the terminal moraines are apt 



to lie parallel to the course of the moraine; the hills of the ground 

 moraine usually trend parallel to the direction of ice movement Asso. 

 elated with the terminal moraines arc many hillocks and abrupt ridges 



of water-worn and assorted gravel and sand, and souk times these water- 

 WTOUghl materials sheathe parte of the moraine where its core is of 

 boulder-clay. 



in low and level tracts the till proper is frequently covered with sand 

 or silt. Many such deposits were made in temporary lakes, accumu- 

 lated between the ice on the one hand and a terminal moraine or higher 

 land on the other. Many such temporary la kes accompanied the reces- 

 sion of the ice sheet, and have left small lacustrine plains to mark their 

 former existence. Lacustrine plains of much greater extent, but due 

 to the same causes, lie in the basins of the Great Lakes, and are trav- 

 ersed by the train in western Ohio and in the neighborhood of Chicago. 



The moraine, first fully and accurately described in America, and 

 which received the designation "kettle moraine," 83 delimits a phase 

 of the great ice sheet in which its margin was divided into lobes, each 

 one a large glacier. Between Newark and Kilbonrn City the route 

 crosses the area overspread by the Scioto, the Mamnee, the Saginaw 

 Bay, the Lake Michigan, and the Green Hay lobes. 



At Kilbourn City, Wis., the line of travel leaves glaciated territory 

 and enters the driftless area 26 of the Upper Mississippi Basin, Thence 

 to La Crosse the topography and the constitution of the surface 

 material stand in sharp contrast to the corresponding features of the 

 region farther east. Rock exposures, which have been rare eastward, 

 and altogether wanting over considerable areas, are here of almost 

 constant occurrence wherever the sin face has any considerable relief. 

 Frequently, too, butte-like hills or fantastically carved, castellated 

 towers of sandstone give some indications of the extent of tile snbaerial 

 erosion the region has suffered. From the presence of these bold 

 eminences within the driftless area, rising 200 or 300 feet above the 

 more or less completely basedeveled plain on which theyrest, ami from 

 their absence in the area covered by ice, instructive inferences may be 

 drawn as to the work effected by the ice in the country over which it 

 passed. Before La Crosse is reached, the bluffs in the immediate vioin 

 ity of the Mississippi are capped with a thin sheet of loess, but this does 

 not attain great thickness east of the Mississippi river in this latitude. 



