KELATIONS OF VALLEY DRIFT AND OTHER DEPOSITS. 475 



into a sheet of gravel extending- across the valley from side to side and not 

 distinguishable from other valley drift. To the south this does not take the 

 form of an osar terrace (broad osar), but is true frontal matter, passing by 

 degrees into finer sediments and finally into marine clays. Here the glacial 

 origin of the valley drift is unmistakable. 



7. That the valley drift is usually more abundant in north-and-soiith 

 than in east-and-west valleys appears to be due wholly to the fact that this 

 was the prevailing direction of the glacial streams. In other words, the 

 law appears to be that where the glacial streams were most active there we 

 find the most valley drift. This gives a distinctly glacial facies to the valley 

 drift. The sizes of the drainage basins, especially of the smaller valleys, 

 often bear no relations to the quantity of the drift. This points distinctly 

 away from the fluviatile hypothesis and toward the g'lacial. 



Summary. — Thcse facts abuudautly prove that overwash plains of glacial 

 sediments formed in front of the ice, and that they are typical valley drift. 

 If tlie glacial hypothesis thus accounts for that portion of the valley drift 

 directly associated with moraines, osars, and other unmistakable glacial 

 phenomena, we need no other hypothesis to account for those sediments 

 that were deposited at longer distances from the ice front of that time, since 

 the latter are what should be expected on that hypothesis. 



RELATIONS OF THE VALLEY DRIFT TO THE OTHER GLACIAL AND THE 

 MARINE SEDIMENTS. 



Comparing the valley drift to the other glacial sediments, we find the 

 following relations : 



Origin. — They all were at one time transported by glacial streams. 



Places of deposition. — Dcposlts withiii ice cliaunels include all the eskers, 

 kames, osars, and border clay of the varieties elsewhere described. 



Deposits poured out in front of the ice by the glacial streams include 

 the following: The marine deltas with most of the marine clays and sands, 

 deposits in fringing or marginal lakes, and overwash aprons or valley drift 

 poured out on land sloping away from the ice front. 



I pause in passing, however, to note that erosion of the till by the 

 sea waves contributed to the marine sands and clays; so, also, water wash 

 from the till contributed to the valley drift. But in both cases the glacial 

 sediments so greatly exceed in quantity the eroded till that jiractically we 

 may speak of both deposits as of glacial origin. 



