ANCIENT KOBUK GEACIER OF ALASKA 89 
one-fourth miles, is made up of irregularly interbanded till and 
modified drift. The latter is an indistinctly stratified sand and fine 
gravel containing many pebbles which yet preserve traces of faceting 
and striation. The till is a blue-gray sandy clay containing many 
striated stones and a few boulders, generally of limestone. The 
smaller rock fragments are mostly schist, limestone, and vein 
quartz, a drift notably differing in composition from that of the penin- 
sula. Any exposed section of the cliff shows one or several bands of 
till 5 to 15 feet thick, occurring in places at the base or top, but 
generally about two-thirds of the distance from the bottom. Where 
at the top, it forms small stony knolls in the rolling upland back of the 
cliff. A portion of the cliff is protected from present erosion by a 
raised beach whose seaward margin is a steep bank rising Io to 15 
feet above the present beach. 
About ten miles farther north there is a mountain range several 
thousand feet high. The gently undulating plain which, near the 
sea-cliff, is beyond doubt a glacial plain, extends inland to the foot 
of this range and a smooth slope extends thence to about midway of 
the height of the range where it appears, in a distant view, to terminate 
abruptly along a line which gently rises and falls, suggesting the 
upper limit of glaciation. Some low ranges of hills that would be 
included in the glaciated area have rather smooth topography but no 
features which of themselves would suggest glaciation. 
On the northern border of the Kobuk Delta there are in places low 
bluffs produced by the most northerly channel of the river swinging 
into a gently undulating upland. Some of this upland country occurs 
southwest of the mouth of this channel and is bordered by a sea-cliff 
on the Hotham Inlet side. I did not land at any of these bluffs and 
cliffs but, seen from a boat, they appear to consist of a thick bed of 
brown and gray sandy silt like that over the till in the peninsula, but 
varying to portions much more largely of sand. The rolling plain 
topography characterizes the lower Kobuk Valley above the delta 
and the country between the delta and the mountains to the north. 
Indeed, as far east as I have been, namely, to the Shungnak River, 
outside of the modern alluvial plain in which the river winds about, 
the valley floor is everywhere an undulating plain rising from 30 to 
200 feet above the river. In the lower valley this plain appears to 
