Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 1 - By Alexander Von Humboldt And Aime Bonpland.
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At The
Hospital Of St. Gothard, Situated Nearly On The Highest Limit Of
The Rhododendron Of The Alps, The Maximum
Of heat, in the month of
August at noon, in the shade, is usually 12 or 13 degrees; in the
Night, at the same season, the air is cooled by the radiation of
the soil down to +1 or-1.5 degrees. Under the same barometric
pressure, consequently at the same height, but thirty degrees of
latitude nearer the equator, the befaria of the Silla is often, at
noon, in the sun, exposed to a heat of 23 or 24 degrees. The
greatest nocturnal refrigeration probably never exceeds 7 degrees.
We have carefully compared the climate, under the influence of
which, at different latitudes, two groups of plants of the same
family vegetate at equal heights above the level of the sea. The
results would have been far different, had we compared zones
equally distant, either from the perpetual snow, or from the
isothermal line of 0 degrees.* (* The stratum of air, the mean
temperature of which is 0 degrees, and which scarcely coincides
with the superior limit of perpetual snow, is found in the parallel
of the rhododendrons of Switzerland at nine hundred toises; in the
parallel of the befarias of Caracas, at two thousand seven hundred
toises of elevation.)
In the little thicket of the Pejual, near the purple-flowered
befaria, grows a heath-leaved hedyotis, eight feet high; the
caparosa,* which is a large arborescent hypericum (* Vismia
caparosa (a loranthus clings to this plant, and appropriates to
itself the yellow juice of the vismia); Davallia meifolia, Heracium
avilae, Aralia arborea, Jacq., and Lepidium virginicum.
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