Alexander von - Personal Narrative of Travels to the Equinoctial Regions of America (Vol.1-3)

We did not quit the farm of Pericantral till after sunset. The south coast of the gulf presents a most fertile aspect, while the northern coast is naked, dry, and rocky. In spite of this aridity, and the scarcity of rain, of which sometimes none falls for the space of fifteen months,* the peninsula of Araya, like the desert of Canound in India, produces patillas, or water-melons, weighing from fifty to seventy pounds. (* The rains appear to have been more frequent at the beginning of the 16th century. At any rate, the canon of Granada (Peter Martyr d'Anghiera), speaking in the year 1574, of the salt-works of Araya, or of Haraia, described in the fifth chapter of this work, mentions showers (cadentes imbres) as a very common phenomenon. The same author, who died in 1526, affirms that the Indians wrought the salt-works before the arrival of the Spaniards. They dried the salt in the form of bricks; and our writer even then discussed the geological question, whether the clayey soil of Haraia contained salt-springs, or whether it had been impregnated with salt by the periodical inundations of the ocean for ages.) In the torrid zone, the vapours contained by the air form about nine-tenths of the quantity necessary to its saturation: and vegetation is maintained by the property which the leaves possess of attracting the water dissolved in the atmosphere.

At sunrise, we saw the Zamuro vultures,* (* Vultur aura.) in flocks of forty or fifty, perched on the cocoa-trees. These birds range themselves in files to roost together like fowls. They go to roost long before sunset, and do not awake till after the sun is above the horizon. This sluggishness seems as if it were shared in those climates by the trees with pinnate leaves. The mimosas and the tamarinds close their leaves, in a clear and serene sky, twenty-five or thirty-five minutes before sunset, and unfold them in the morning when the solar disk has been visible for an equal space of time. As I noticed pretty regularly the rising and setting of the sun, for the purpose of observing the effect of the mirage, or of the terrestrial refractions, I was enabled to give continued attention to the phenomena of the sleep of plants. I found them the same in the steppes, where no irregularity of the ground interrupted the view of the horizon. It appears, that, accustomed during the day to an extreme brilliancy of light, the sensitive and other leguminous plants with thin and delicate leaves are affected in the evening by the smallest decline in the intensity of the sun's rays; so that for vegetation, night begins there, as with us, before the total disappearance of the solar disk. But why, in a zone where there is scarcely any twilight, do not the first rays of the sun stimulate the leaves with the more strength, as the absence of light must have rendered them more susceptible? Does the humidity deposited on the parenchyma by the cooling of the leaves, which is the effect of the nocturnal radiation, prevent the action of the first rays of the sun? In our climates, the leguminous plants with irritable leaves awake during the twilight of the morning, before the sun appears.

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