370 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
Hunker and Bonanza Creeks, there is a series of deep gravels covered 
with soil and peat moss and containing the remains of extinct and 
existing animals in large quantities. Bones of mastodon and huge 
mammoth tusks, skulls of buffaloes and bones of bear, musk ox, and 
mountain sheep, as well as ancient beaver dams, are often discovered 
by the drift miners. These ancient denizens of the valleys must some- 
times have been of immense size. I met a digger from another gold 
field in Alaska who told me that he had once seen a mammoth’s tusk 
14 feet long in the frozen gravel, but those found in the Klondike dis- 
trict have seldom a length of more than 11 or 12 feet. 
In these gulch or valley gravels the richest gold is found, and the 
most valuable part is at the bottom next the bedrock. To reach the 
pay streak shafts have to be sunk where the gravel is deep, and the 
fact that the ground is all frozen makes the drift mining a compara- 
tively easy operation requiring very little timbering or pumping. 
The second set of auriferous gravels occurs at certain places on high 
terraces or benches cut in the rock, and they reach up to about 450 
feet above the beds of the existing valleys. These high-level gravels 
are mostly white or pale in color, very compact, and quite different in 
appearance from the loose and more recently formed low-level placer 
deposits. They are largely made up of white quartz pebbles and 
sand and subangular pieces of vein quartz and sericite schist. The 
largest bowlders are seldom more than 18 inches in diameter except 
near the bottom, where large angular blocks 3 or 4 feet in diameter 
are occasionally found. The white channel gravel is very uniform in 
texture and reaches a thickness at places of 150 feet, with a maximum 
width of more than a mile. It is almost unstratified and, unlike the 
valley gravel, is totally destitute of plant or animal remains. At the 
bottom of the white gravel there is a pay streak next the rock. This 
is at places extremely rich, but gold occurs throughout the whole bed 
in quantities sufficient to be profitably extracted by hydraulicking, 
but not by individual miners. The best of the pay streak has been 
already exhausted by drifting, and what is left is bemg worked by 
hydraulic ‘‘giants’”’ in the hands of capitalists. 
These two distinct river deposits have an interesting story to tell. 
They point unmistakably to a change in the level of the land at one 
period, and indeed when the Yukon territory comes to be better 
explored many other interesting historical points that are now obscure 
will be cleared up. There is evidence of a considerable change in sey- 
eral parts of the Yukon River system since the Tertiary period, and 
some of the rivers have been able to capture parts of others and so 
modify the original pattern of the continental drainage. The land 
has not remained quite stationary, and indeed in Yakutat Bay, in 
Alaska, as recently as 1899, there was a terrific earthquake, accom- 
