154 The American Geologist. March, 1903. 
have obtained since, and the field evidence so clearly connects 
this short alluvial fan-forming period with the early stages of 
the glaciation that I feel that it is reasonable to assume one 
general cause for both in which a higher average humidity may 
have played an important part. We usually associate the idea 
of cloud-burst with that of desert conditions, but in the pres- 
ence of evidence that in the early stages of glaciation in the 
Salmon river valley, there was suddenly formed by abnormal 
precipitation a series of alluvial fans which deranged the 
drainage, I will disregard all precedents. 
The gorge above Cooper's mine is, if my interpretation is 
correct, the measure of the time since the early stages of the 
glaciers. It is about one mile in length. The depth near the 
lower end is about 300 feet of which probably 150 feet is the 
amount of rock cutting since the rearrangement of the drain- 
age. Along the central portion of the gorge it is a "box 
canon" (having nearly perpendicular walls) and trenched 
about 150 feet into the rock. Near the head it is in places but 
twenty to thirty feet wide and fifty to seventy-five feet deep. 
Here the river descends by a series of cascades, seventy-five 
feet in less than 300 feet of distance. The total descent of the 
river within the gorge is about 350 feet. The bottom of the 
canon is nowhere much wider than the river. The southern 
side of an unclimbable rock wall almost from end to end. Over 
this there cascade in rainy weather streams from the moun- 
tain slope above. 
Salmon river in passing the gorge contains the drainage 
of about twelve square miles. Late in summer it dwindles 
to several hundred miners' inches, but during the greater part 
of the year averages 10,000 inches. In several short flood per- 
iods each year it is a mighty torrent carrying- probabl}- many 
score thousands of miners' inches of water. 
It is natural to suppose that a river of this character would 
erode its bed rapidly but in refutation of that idea I have the 
following evidence : The rock excavated is hornblende schist, 
one of the most resistant of formations. In this respect it will 
probably compare with any rock that I have seen post-glacially 
caiioned in the Mississippi basin — for instance, below Niagara 
and St. Anthony falls — as ten to one. The river is nearly all 
the year "as clear as crystal" and there is no fine sediment to 
