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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The Centigrade Thermometer, At A Distance From The
Ground, And From The Apertures That Emitted The Hot Vapours, Fell
In The Shade To 2.7 Degrees.
The wind was west, and consequently
opposite to that which brings to Teneriffe, during a great part of
the year, the warm air that floats above the burning desert of
Africa.
As the temperature of the atmosphere, observed at the port
of Orotava by M. Savagi, was 22.8 degrees, the decrement of caloric
was one degree every 94 toises. This result perfectly corresponds
with those obtained by Lamanon and Saussure on the summits of the
Peak and Etna, though in very different seasons. The tall slender
form of these mountains facilitates the means of comparing the
temperature of two strata of the atmosphere, which are nearly in
the same perpendicular plane; and in this point of view the
observations made in an excursion to the volcano of Teneriffe
resemble those of an ascent in a balloon. We must nevertheless
remark, that the ocean, on account of its transparency and
evaporation, reflects less caloric than the plains, into the upper
regions of the air; and also that summits which are surrounded by
the sea are colder in summer, than mountains which rise from a
continent; but this circumstance has very little influence on the
decrement of atmospherical heat; the temperature of the low regions
being equally diminished by the proximity of the ocean.
It is not the same with respect to the influence exercised by the
direction of the wind, and the rapidity of the ascending current;
the latter sometimes increases in an astonishing manner the
temperature of the loftiest mountains.
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