Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 1 - By Alexander Von Humboldt And Aime Bonpland.
- Page 401 of 407 - First - Home
We Seemed To Be
Transported To The Most Industrious Districts Of Catalonia.
Near
San Mateo we find the last fields of wheat, and the last mills with
horizontal hydraulic wheels.
A harvest of twenty for one was
expected; and, as if that produce were but moderate, I was asked
whether corn yielded more in Prussia and in Poland. By an error
generally prevalent under the tropics, the produce of grain is
supposed to degenerate in advancing towards the equator, and
harvests are believed to be more abundant in northern climates.
Since calculations have been made on the progress of agriculture in
the different zones, and on the temperatures under the influence of
which corn will flourish, it has been found that, beyond the
latitude of 45 degrees, the produce of wheat is nowhere so
considerable as on the northern coasts of Africa, and on the
table-lands of New Grenada, Peru, and Mexico. Without comparing the
mean temperature of the whole year, but only the mean temperature
of the season which embraces the corn cycle of vegetation, we find
for three months of summer,* in the north of Europe, from 15 to 19
degrees; in Barbary and in Egypt, from 27 to 29 degrees; within the
tropics, between fourteen and three hundred toises of height, from
14 to 25.5 degrees of the centigrade thermometer. (* The mean heat
of the summers of Scotland in the environs of Edinburgh, (latitude
56 degrees), is found again on the table-lands of New Grenada, so
rich in wheat, at 1400 toises of elevation, and at 4 degrees north
latitude. On the other hand, we find the mean temperature of the
valleys of Aragua, latitude 10 degrees 13 minutes, and of all the
plains which are not very elevated in the torrid zone, in the
summer temperature of Naples and Sicily, latitude 39 to 40 degrees.
These figures indicate the situation of the isotheric lines (lines
of the same summer heat), and not that of the isothermal lines
(those of equal annual temperature). Considering the quantity of
heat received on the same spot of the globe during a whole year,
the mean temperatures of the valleys of Aragua, and the table-lands
of New Grenada, at 300 and 1400 toises of elevation, correspond to
the mean temperatures of the coasts at 23 and 45 degrees of
latitude.)
The fine harvests of Egypt and of Algiers, as well as those of the
valleys of Aragua and the interior of the island of Cuba,
sufficiently prove that the augmentation of heat is not prejudicial
to the harvest of wheat and other alimentary grain, unless it be
attended with an excess of drought or moisture. To this
circumstance no doubt we must attribute the apparent anomalies
sometimes observed within the tropics, in the lower limit of corn.
We are astonished to see, eastward of the Havannah, in the famous
district of Quatro Villas, that this limit descends almost to the
level of the ocean; whilst west of the Havannah, on the slope of
the mountains of Mexico and Xalapa, at six hundred and
seventy-seven toises of height, the luxuriance of vegetation is
such, that wheat does not form ears.
Enter page number
PreviousNext
Page 401 of 407
Words from 208078 to 208610
of 211363
