356 The Glacial Theory of Prof. Agassiz. 
not permit us to suppose that any cascade could ever have existed. In 
other cases, a long, sinuous, dry, water-worn gutter or channel is ob- 
served, the course of which runs across, instead of along, the natural 
declivity of the ground. The study of the glaciers has enabled Agas- 
siz to find a key to these enigmatical phenomena, which had perplexed 
previous inquirers. Streams of water flow along the surface of a gla- 
cier, and when one of these falls into a fissure which is open to the bot- 
tom, it often forms a cascade, and cuts a round cavity in the rock with the 
gravel and sand which it either finds there, or carries down with it, as 
some of our rivulets work out the hollows termed cauldrons. When no 
fissure exists, the stream sometimes cuts a funnel or shaft (couloir, en- 
tonnoir) through the ice by the action of gravel. If the glacier is trav- 
elling downwards, the cascade will travel with it, and convert the round 
cavity in the rock into a long gutter; or, supposing the water to reach 
the bottom without falling in a cascade, still, in finding an issue below 
the glacier, it will be compelled to follow the sinuous openings left by 
inequalities in the bottom of the ice, and thus take a course at variance 
with the natural inclination of the surface. We have here an explana- 
tion of the creux, or holes, and the long water-worn gutters found in 
such unlikely situations, which bear the local names of lapiaz orkarren. . 
These are chiefly observed where the rock is soft, and are seldom vis¢ 
ible on the granite. 
Stratified Gravel on sides of Valleys—When a small peutial of 
stratified gravel or sand is found adhering to the side of a valley, high 
above its bottom, the conclusion usually come to is, that a lake or arm 
of the sea had once filled the whole up to that level, and that the de- 
posit is merely a remnant of one much more extensive. has 
shown that this conclusion may be erroneous. When the streamlets 
flowing on or under a glacier, cannot find an escape below, they often 
form small lakes at the surface on its flanks, and, as in other lakes, the 
gravel and sand carried into these, arrange themselves in strata. This 
stratified deposit may be continuous with, and form as it were a portion 
‘of, a lateral moraine, which is not only unstratified, but which follows 
a line probably far from level. Here again the _— of existing ~ 
eiers enables us to explain very anomalous ap i 
eae - Glacier Barriers —A glacier descending a a‘ opening into an- 
other, Sometimes pushes forward till it forms a dike or barrier across 
ovleinen: Behind this the water collects and constitutes a lake, which 
sments till it breaks the icy barrier, or flows over it, producing fright- 
ful inundations. In 1815 the glacier nt Getroz formed a dike across 
the valley of Bagnes, sf ike went on increasing till 1818, when 
it was 500 feet” hgh and 80 long Tw noe then burst by. the pressure 
of the waters of the Drance. 1 terrible ravages as far 
nS fay 
