192 The American Geologist. March, 1892 
becomes choked, and the sub-glacial waters are forced to find a 
new outlet. 
In the case of the stream issuing from the Atrevida glacier, the 
channel is deeply filled with débris, most of it of large size, de- 
rived from the ice cliffs near its source, but the water is swift and 
the boulders are swept along the channel until they can find a 
resting place. . When near the stream, one may hear, even above 
the roar of the torrent, the clashing and pounding of the boulders 
as they are rolled along and hit against each other or against the 
still larger stones over which the water rushes. As soon as the 
canon widens, the stream divides and piles up the boulders, now 
on one side of its channel and now on the other, while the finer 
material is carried farther down. Owing to the deposition of the 
coarser portion of the heavy load with which the stream starts, its 
channel is built up higher than the adjacent surface, and conse- 
quently the drainage is unstable. Some three miles from its 
source the stream passes a spur of hills on its left and has room 
to expand its deposits. It then bifurcates again and again, and 
is constantly forming new channels. The region through which 
the stream flows is heavily timbered and the expansion of the tor 
rent-swept area is accomplished by invading the forest on either 
side of its course. Where this has occurred recently, the dead 
trees are still standing, and in some instances even retain their 
withered foliage; farther out in the gravel deposit they are dead 
but unbroken; while still farther away, only trunks and stumps 
project above the barren, stream-swept surface. The dé- 
bris thus being laid down has the form of a segment of a low 
cone. The apex of the cone is four or five miles from its base, 
on Yakutat bay, and has an elevation of some six or eight hun- 
dred feet. Its breadth near its base is about two miles. The 
depth of the deposit cannot be determined, as building is in active 
progress and dissection has not begun, but judging from the con- 
tour of the adjacent surface, is must be several hundred feet in 
the central portion. The deposit is coarse and sub-angular near 
the apex of the cone, boulders four feet in diameter being not un- 
common, but become finer and finer near its base. The outer 
portion of the deposit, near Yakutat bay, is composed of gravel 
and sand, From the mode of its formation and the character of 
its surface, it is safe to assure that it is cross-stratified through- 
out and has many abrupt alternations of fine and coarse material. 
