CONTENTS. IX 



Chapter VI. — CLissificatiou of the glacial sediments of Maine — Continued. Page. 



Systems of iliscontimious osars - - 376 



Glacial gravels of the coastal region 379 



Relations of glacial gravels t® the fossiliferous marine beds 379 



Lenticular shape of the coastal gravel masses 382 



Decrease of glacial gravels toward the coast 386 



Summary 389 



Eetreatal phenomena 390 



Causes of noncontinuous sedimentation -svithin ice channels , 395 



R^sum^: History of the coastal gravels 403 



Late glacial history of the coastal region 409 



Summary 411 



Osars 413 



Comparison of continuous with discontinuous osars 416 



"Were osars deposited by subgiacial or hy superficial streams? 420 



Length of ridge .-- 421 



Angle of lateral slope of the ridges 423' 



Internal structure 423 



Meanderings of a ridge 425 



Pinnacles or elongated cones 426 



Broad and massive enlargements 427 



Reticulated ridges 427 



Probable velocities of the two kinds of streams 428 



Erosion of the ground moraine 429 



Gaps in the osars 430 



Size of the osars 431 



Local versus far- traveled material 431 



Phenomena of glacial rivers in crossing hills and valleys 433 



Broad osars or osar terraces 440 



Formation of the broad osar channels. 444 



Reticulated eskers or kauies 448 



Ways in which a ridge of aqueous sediment can be formed 451 



Formation of kettleholes and other basins inclosed by ridges or by plains of aqueous 



sediments 453 



Origin of the glacial gravel complex and its relation to marine and lacustral deltas 455 



Plexus situated at one end of a marine glacial delta 455 



Reticulated ridges at the proximal ends of the glacial lacustrine deltas 459 



Reticulated ridges as a part of glacial lacustrine massives 459 



Reticulated ridges within ice channels 460 



Origin of the larger complexes - 463 



Osar border clay 468 



Deltas deposited by glacial streams in frontal glacial lakes-- 469 



Valley drift 4™ 



Valley drift of purely fliiviatile origin 470 



Valley drift of semiglacial origin 474 



Relation of the valley drift to the other glacial and marine sediments 475 



Historical relations - 476 



Relation of the valley drift to the marine beds 480 



Former height of the sea : • 481 



Causes of the relative fineness of the lower strata of the valley drift and the marine 



beds of the interior valleys 485 



The lower stratum, composed of clay, silt, or fine sand 485 



The coarser upper stratum ' 486 



Sizes of the valley-drift rivers 488- 



Index *91 



