On The Climate And Productions Of Tierra Del Fuego And
Of The South-West Coast.
- The following table gives the
mean temperature of Tierra del Fuego, the Falkland Islands,
and, for comparison, that of Dublin:
-
Summer Winter Mean of Summer
Latitude Temp. Temp. and Winter
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Tierra del Fuego 53 38' S. 50 33.08 41.54
Falkland Islands 51 38' S. 51 - -
Dublin 53 21' N. 59.54 39.2 49.37
Hence we see that the central part of Tierra del Fuego is
colder in winter, and no less than 9.5 degs. less hot in
summer, than Dublin. According to von Buch, the mean
temperature of July (not the hottest month in the year)
at Saltenfiord in Norway, is as high as 57.8 degs.,
and this place is actually 13 degs. nearer the pole
than Port Famine! [8] Inhospitable as this climate appears
to our feelings evergreen trees flourish luxuriantly under
it. Humming-birds may be seen sucking the flowers, and
parrots feeding on the seeds of the Winter's Bark, in lat.
55 degs. S. I have already remarked to what a degree the
sea swarms with living creatures; and the shells (such as
the Patellae, Fissurellae, Chitons, and Barnacles),
according to Mr. G. B. Sowerby, are of a much larger size
and of a more vigorous growth, than the analogous species in
the northern hemisphere. A large Voluta is abundant in
southern Tierra del Fuego and the Falkland Islands. At
Bahia Blanca, in lat. 39 degs. S., the most abundant shells were
three species of Oliva (one of large size), one or two Volutas,
and a Terebra. Now, these are amongst the best characterized
tropical forms. It is doubtful whether even one
small species of Oliva exists on the southern shores of
Europe, and there are no species of the two other genera.
If a geologist were to find in lat 39 degs. on the coast of
Portugal a bed containing numerous shells belonging to three
species of Oliva, to a Voluta and Terebra, he would probably
assert that the climate at the period of their existence must
have been tropical; but judging from South America, such an
inference might be erroneous.
The equable, humid, and windy climate of Tierra del
Fuego extends, with only a small increase of heat, for many
degrees along the west coast of the continent. The forests
for 600 miles northward of Cape Horn, have a very similar
aspect. As a proof of the equable climate, even for 300 or
400 miles still further northward, I may mention that in
Chiloe (corresponding in latitude with the northern parts
of Spain) the peach seldom produces fruit, whilst strawberries
and apples thrive to perfection. Even the crops of
barley and wheat [9] are often brought into the houses to be
dried and ripened. At Valdivia (in the same latitude of
40 degs., with Madrid) grapes and figs ripen, but are not
common; olives seldom ripen even partially, and oranges not at
all. These fruits, in corresponding latitudes in Europe, are
well known to succeed to perfection; and even in this continent,
at the Rio Negro, under nearly the same parallel
with Valdivia, sweet potatoes (convolvulus) are cultivated;
and grapes, figs, olives, oranges, water and musk melons,
produce abundant fruit. Although the humid and equable
climate of Chiloe, and of the coast northward and southward
of it, is so unfavourable to our fruits, yet the native
forests, from lat. 45 to 38 degs., almost rival in luxuriance
those of the glowing intertropical regions. Stately trees of
many kinds, with smooth and highly coloured barks, are loaded
by parasitical monocotyledonous plants; large and elegant
ferns are numerous, and arborescent grasses entwine the
trees into one entangled mass to the height of thirty or forty
feet above the ground. Palm-trees grow in lat 37 degs.; an
arborescent grass, very like a bamboo, in 40 degs.; and
another closely allied kind, of great length, but not erect,
flourishes even as far south as 45 degs. S.
An equable climate, evidently due to the large area of sea
compared with the land, seems to extend over the greater
part of the southern hemisphere; and, as a consequence, the
vegetation partakes of a semi-tropical character. Tree-ferns
thrive luxuriantly in Van Diemen's Land (lat. 45 degs.), and I
measured one trunk no less than six feet in circumference.
An arborescent fern was found by Forster in New Zealand
in 46 degs., where orchideous plants are parasitical on the
trees. In the Auckland Islands, ferns, according to Dr.
Dieffenbach [10] have trunks so thick and high that they may
be almost called tree-ferns; and in these islands, and even
as far south as lat. 55 degs. in the Macquarrie Islands,
parrots abound.
On the Height of the Snow-line, and on the Descent of
the Glaciers in South America. - For the detailed authorities
for the following table, I must refer to the former edition: -
Height in feet
Latitude of Snow-line Observer
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Equatorial region; mean result 15,748 Humboldt.
Bolivia, lat. 16 to 18 degs. S. 17,000 Pentland.
Central Chile, lat. 33 degs. S. 14,500 - 15,000 Gillies, and
the Author.
Chiloe, lat. 41 to 43 degs. S. 6,000 Officers of the
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.
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