T ‘7
■ á| ii
found much further northward: and considering the immense
size of the one just described, it is extremely improbable
that it should be the last. On the island of Chiloe, which
fronts the Cordillera as the Jura does the Alps, many angular
fragments of granite, of an enormous size, which appear
to have crossed the inland arm of sea, lie scattered at
different heights over the country. Although situated between
the parallels of 41° and 43°, I know of no sound
objection to the supposition that these might formerly have
been floated across, on icebergs produced by the fall of glaciers.
We are not bound to suppose that the latitude 46° 40' has
always been the northern limit of such phenomena, even if it
should be so at present. AVe have endeavoured to show that
the snow-line in the parallel of Chiloe has an elevation of
about 6000 fe e t; and since on Mont Blanc the glaciers descend
5160 feet beneath the line of perpetual snow, we might
at present expect to find them in front of Chiloe at a very
small altitude above the level of the sea.
With respect to the position of the glaciers, they seem
to occur only within the deep sounds which penetrate the
central Cordillera. This may be attributed chiefly to the
subordinate elevation of the outer lines. When we consider
the vast dimensions and number of these glaciers, the effect
produced on the land must he very great. Every one has
heard of the mass of rubbish propelled by the glaciers of
Switzerland, as they slowly creep onwards. In the same
manner in Tierra del Fuego, on a still night the cracking and
groaningof the great movingmassmay be distinctly heard. The
same force, whioh is known to uproot whole forests of lofty
trees, must, when grating over the surface, tear from the
flanks of the mountain many huge fragments of rock. Beneath
each glacier, also, a roaring torrent drains the upper
part of the ice. To these effects, which are common to all
cases, there must be added, in this country, the wear and
tear of the waves produced by each successive fall. Nor can
this agency be inconsiderable, when we remember that it
goes on night and day, century after century. AA’e must look
at every portion of the mountain as having, during the gradual
rising of the land, been successively exposed to the action
of these combined forces.
It is, perhaps, useless to speculate on the effects of earthquakes
without some positive data. But as we find in the
immediate neighbourhood of that great glacier, which stands
in the latitude of the Alps, Byron* mentioning with surprise
the quantities of sea-shells lying on aU the hill-tops (a fact
which may be taken as a proof of recent continental elevations)
; and Bulkeley,! in his narrative, saying, “ This day
we felt four great earthquakes, three of which were very
terrible;” we may feel weU assured, that the same power,
which in Chile causes such vast masses of rock and soil to fall
from the sea-cliffs, has oftentimes precipitated fragments far
more immense, of a mass traversed by great fissures, already
in motion, and resting on an inclined plane. I cannot imagine
any scene of more terrific violence, than the waves produced
by such a fall : we know that they are very had from the
mere oscillation, consequent on the movements of the ground ;
but in this case I can readily believe that the water would be
fairly beaten back out of the deepest inlet, and then returning
with an overwhelming force, would whirl about rocks of
vast size like so much chaff.
In after ages, with a climate modified by the process of
such physical changes as are now going on throughout the
greater part of this continent, the effects which had been produced
by these glaciers would appear inexplicable, to a person
who doubted the possibility of their occurrence in such latitudes.
He would see in the most retired and protected valleys
(the present channels) beaches composed of great
rounded boulders, such as those heaped up on the shore of
the most turbulent ocean. Then perhaps he would speculate,
either that the outer chain of mountains had been elevated
* B y ro n ’s NarratÌA’e o f th e S h ipw r e c k o f th e W a g e r ,
t B u lk e le y ’s a n d C um m in ’s F a i th f u l N a r r a tiv e o f th e loss o f th e W a g e r .
T h e e a r th q u a k e h a p p e n e d A u g u s t 2.5, 1 7 4 1 .
m
I
i' lì
I ,