Tropical nature, and other essaysWallace, Alfred Russel
History
Tropical nature, and other essays
Wallace, Alfred Russel
Ecology -- Tropics; Natural history -- Tropics; Tropics
_The Aspect of the Equatorial Heavens._--Within the limits of the
equatorial zone the noonday sun is truly vertical twice every
year, and for several months it passes so near the zenith that the
difference can hardly be detected without careful observation of
the very short shadows of vertical objects. The absence of distinct
horizontal shadows at noon which thus characterises a considerable
part of the year, is itself a striking phenomenon to an inhabitant
of the temperate zones; and equally striking is the changed aspect
of the starry heavens. The grand constellation Orion, passes
vertically overhead, while the Great Bear is only to be seen low
down in the northern heavens, and the Pole star either appears
close to the horizon or has altogether disappeared according as we
are north or south of the equator. Towards the south the Southern
Cross, the Magellanic clouds, and the jet-black “coal sacks” are the
most conspicuous objects invisible in our northern latitudes. The
same cause that brings the sun overhead in its daily march equally
affects the planets, which appear high up towards the zenith far
more frequently than with us, thus affording splendid opportunities
for telescopic observation.
_Intensity of Meteorological Phenomena at the Equator._--The
excessive violence of meteorological phenomena generally supposed to
be characteristic of the tropics is not by any means remarkable in
the equatorial zone. Electrical disturbances are much more frequent,
but not generally more violent than in the temperate regions. The
wind-storms are rarely of excessive violence, as might in fact be
inferred from the extreme steadiness of the barometer, whose daily
range at Batavia rarely exceeds one-eighth of an inch, while the
extreme range during three years was less than one-third of an inch!
The amount of the rainfall is very great, seventy or eighty inches
in a year being a probable average; and as the larger part of this
occurs during three or four months, individual rainfalls are often
exceedingly heavy. The greatest fall recorded at Batavia during
three years was three inches and eight-tenths in one hour,[4] but
this was quite exceptional, and even half this quantity is very
unusual. The greatest rainfall recorded in twenty-four hours is
seven inches and a quarter; but more than four inches in one day
occurs only on two or three occasions in a year. The blue colour
of the sky is probably not so intense as in many parts of the
temperate zone, while the brilliancy of the moon and stars is not
perceptibly greater than that of our clearest frosty nights, and
is undoubtedly much inferior to what is witnessed in many desert
regions, and even in Southern Europe.
[4] On January 10th, 1867, from 1 to 2 A.M.
On the whole, then, we must decide, that uniformity and abundance,
rather than any excessive manifestations, are the prevailing
characteristic of all the climatal phenomena of the equatorial zone.
Public-domain text, read in full here on John Shaqi.
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