GLACIATION OF THE ALASKA RANGE 417 
under Captain E. F. Glenn, crossed Delta Pass. Since that year 
geologic and topographic surveys have gradually been extended 
until only small portions of the range are now unknown. Captain 
Herron, in 1899, discovered Simpson Pass at the head of Kichitna 
River, and explored a portion of the Kuskokwim lowland. In 
1902 Brooks and Prindle* traversed the range at Rainy Pass and 
followed the north slope of the mountains between Kuskokwim and 
Nenana rivers, and in the same year a topographic and geologic 
map? was made of the south slope between Delta and Mentasta 
passes. In 1903 Dr. F. A. Cook organized a party for the ascent 
of Mount McKinley from the northwest. The route already estab- 
lished by Brooks and Prindle from Tyonek to the head of the 
Skwentna, and thence along the northwest base of the mountains, 
was followed as far as Muldrow Glacier. From that point the 
party proceeded in an eastward direction, discovered a pass across 
a glacier, and emerged on the headwaters of Chulitna River. In 
1906 a topographic map was made by R. W. Porter of a portion of 
the northwest border of Susitna basin. In 1910 the area on the 
north of the range between Nenana and Delta rivers was mapped! 
geologically and topographically, as was a portion of the range south 
of this, and during that same summer some explorations were 
carried on in the high range southeast of Mount McKinley by a 
party under the leadership of Herschel Parker and Belmore Brown. 
In tort a portion of the northwest border of the Susitna basin was 
visited by the writer.° This gradual completion of reconnaissance 
surveys has added to our knowledge of the geography of the region 
until the time seems ripe to summarize briefly the facts with regard 
1A. H. Brooks and L. M. Prindle, “‘The Mt. McKinley Region, Alaska,” Prof. 
Paper U.S. Geol. Survey No. 70, tott. 
2,W. C. Mendenhall, “Geology of the Central Copper River Region, Alaska,’’ 
Prof. Paper U.S. Geol. Survey No. 41, 1906. 
3 Published in “The Mt. McKinley Region, Alaska,” Prof. Paper U.S. Geol. 
Survey No. 70, 19it. Z 
4S. R. Capps, “The Bonnifield Region, Alaska,”? Bull. U.S. Geol. Survey No. 501, 
IQ12. 
5F. H. Moffit, ‘‘Headwater Regions of Gulkana and Susitna Rivers, Alaska,” 
Bull. U.S. Geol. Survey No. 498, 1912. 
6 “The Yentna Region, Alaska,” Bull. U.S. Geol. Survey. In preparation. 
