Beagle and the
Author.
Tierra del Fuego, 54 degs. S. 3,500 - 4,000 King.
As the height of the plane of perpetual snow seems chiefly to be
determined by the extreme heat of the summer, rather than by the mean
temperature of the year, we ought not to be surprised at its descent in
the Strait of Magellan, where the summer is so cool, to only 3500 or
4000 feet above the level of the sea; although in Norway, we must
travel to between lat. 67 and 70 degs. N., that is, about 14 degs.
nearer the pole, to meet with perpetual snow at this low level. The
difference in height, namely, about 9000 feet, between the snow-line on
the Cordillera behind Chiloe (with its highest points ranging from only
5600 to 7500 feet) and in central Chile [11] (a distance of only 9
degs. of latitude), is truly wonderful. The land from the southward of
Chiloe to near Concepcion (lat. 37 degs.) is hidden by one dense forest
dripping with moisture. The sky is cloudy, and we have seen how badly
the fruits of southern Europe succeed. In central Chile, on the other
hand, a little northward of Concepcion, the sky is generally clear,
rain does not fall for the seven summer months, and southern European
fruits succeed admirably; and even the sugar-cane has been cultivated.
[12] No doubt the plane of perpetual snow undergoes the above
remarkable flexure of 9000 feet, unparalleled in other parts of the
world, not far from the latitude of Concepcion, where the land ceases
to be covered with forest-trees; for trees in South America indicate a
rainy climate, and rain a clouded sky and little heat in summer.
The descent of glaciers to the sea must, I conceive, mainly depend
(subject, of course, to a proper supply of snow in the upper region) on
the lowness of the line of perpetual snow on steep mountains near the
coast. As the snow-line is so low in Tierra del Fuego, we might have
expected that many of the glaciers would have reached the sea.
Nevertheless, I was astonished when I first saw a range, only from 3000
to 4000 feet in height, in the latitude of Cumberland, with every
valley filled with streams of ice descending to the sea-coast. Almost
every arm of the sea, which penetrates to the interior higher chain,
not only in Tierra del Fuego, but on the coast for 650 miles
northwards, is terminated by "tremendous and astonishing glaciers," as
described by one of the officers on the survey. Great masses of ice
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