We could observe by the chronometer the moment when the disk of the sun touched the horizon of the sea. The first contact was at 6 hours 8 minutes 13 seconds; the second, at 6 hours 10 minutes 26 seconds; mean time. This observation, which is not unimportant for the theory of terrestrial refractions, was made on the summit of the mountain, at the absolute height of 296 toises. The setting of the sun was attended by a very rapid cooling of the air. Three minutes after the last apparent contact of the disk with the horizon of the sea, the thermometer suddenly fell from 25.2 to 21.3 degrees. Was this extraordinary refrigeration owing to some descending current? The air was however calm, and no horizontal wind was felt.
We passed the night in a house where there was a military post consisting of eight men, under the command of a Spanish serjeant. It was an hospital, built by the side of a powder magazine. When Cumana, after the capture of Trinidad by the English, in 1797, was threatened with an attack, many of the inhabitants fled to Cumanacoa, and deposited whatever articles of value they possessed in sheds hastily constructed on the top of the Imposible. It was then resolved, in case of any unforeseen invasion, to abandon the castle of San Antonio, after a short resistance, and to concentrate the whole force of the province round the mountains, which may be considered as the key of the Llanos.
The top of the Imposible, as nearly as I could perceive, is covered with a quartzose sandstone, free from petrifactions. Here, as on the ridge of the neighbouring mountains, the strata pretty regularly take the direction from north-north-east to south-south-west. This direction is also most common in the primitive formations in the peninsula of Araya, and along the coasts of Venezuela. On the northern declivity of the Imposible, near the Penas Negras, an abundant spring issues from sandstone, which alternates with a schistose clay. We remarked on this point fractured strata, which lie from north-west to south-east, and the dip of which is almost perpendicular.
The Llaneros, or inhabitants of the plains, send their produce, especially maize, leather, and cattle, to the port of Cumana by the road over the Imposible. We continually saw mules arrive, driven by Indians or mulattoes. Several parts of the vast forests which surround the mountain, had taken fire. Reddish flames, half enveloped in clouds of smoke, presented a very grand spectacle. The inhabitants set fire to the forests, to improve the pasturage, and to destroy the shrubs that choke the grass. Enormous conflagrations, too, are often caused by the carelessness of the Indians, who neglect, when they travel, to extinguish the fires by which they have dressed their food. These accidents contribute to diminish the number of old trees in the road from Cumana to Cumanacoa; and the inhabitants observe justly, that, in several parts of their province, the dryness has increased, not only because every year the frequency of earthquakes causes more crevices in the soil; but also because it is now less thickly wooded than it was at the time of the conquest.
I arose during the night to determine the latitude of the place by the passage of Fomalhaut over the meridian; but the observation was lost, owing to the time I employed in taking the level of the artificial horizon. It was midnight, and I was benumbed with cold, as were also our guides: yet the thermometer kept at 19.7 degrees. At Cumana I have never seen it sink below 21 degrees; but then the house in which we dwelt on the Imposible was 258 toises above the level of the sea. At the Casa de la Polvora I determined the dip of the magnetic needle, which was 42.5 degrees.* (* The magnetic dip is always measured in this work, according to the centesimal division, if the contrary be not expressly mentioned.) The number of oscillations correspondent to 10 minutes of time was 233. The intensity of the magnetic forces had consequently augmented from the coast to the mountain, perhaps from the influence of some ferruginous matter, hidden in the strata of sandstone which cover the Alpine limestone.
We left the Imposible on the 5th of September before sunrise. The descent is very dangerous for beasts of burden; the path being in general but fifteen inches broad, and bordered by precipices. In descending the mountain, we observed the rock of Alpine limestone reappearing under the sandstone. The strata being generally inclined to the south and south-east, a great number of springs gush out on the southern side of the mountain. In the rainy season of the year, these springs form torrents, which descend in cascades, shaded by the hura, the cuspa, and the silver-leaved cecropia or trumpet-tree.
The cuspa, a very common tree in the environs of Cumana and of Bordones, is yet unknown to the botanists of Europe. It was long used only for the building of houses, and has become celebrated since 1797, under the name of the cascarilla or bark-tree (cinchona) of New Andalusia. Its trunk rises scarcely above fifteen or twenty feet. Its alternate leaves are smooth, entire, and oval.* (* At the summit of the boughs, the leaves are sometimes opposite to each other, but invariably without stipules.) Its bark very thin, and of a pale yellow, is a powerful febrifuge. It is even more bitter than the bark of the real cinchona, but is less disagreeable. The cuspa is administered with the greatest success, in a spirituous tincture, and in aqueous infusion, both in intermittent and in malignant fevers.
On the coasts of New Andalusia, the cuspa is considered as a kind of cinchona; and we were assured, that some Aragonese monks, who had long resided in the kingdom of New Grenada, recognised this tree from the resemblance of its leaves to those of the real Peruvian bark-tree. This, however, is unfounded; since it is precisely by the disposition of the leaves, and the absence of stipules, that the cuspa differs totally from the trees of the rubiaceous family. It may be said to resemble the family of the honeysuckle, or caprifoliaceous plants, one section of which has alternate leaves, and among which we find several cornel-trees, remarkable for their febrifuge properties.* (* Cornus florida, and C. sericea of the United States.—Walker on the Virtues of the Cornus and the Cinchona compared. Philadelphia 1803.)
The taste, at once bitter and astringent, and the yellow colour of the bark led to the discovery of the febrifugal virtue of the cuspa. As it blossoms at the end of November, we did not see it in flower, and we know not to what genus it belongs; and I have in vain for several years past applied to our friends at Cumana for specimens of the flower and fruit. I hope that the botanical determination of the bark-tree of New Andalusia will one day fix the attention of travellers, who visit this region after us; and that they will not confound, notwithstanding the analogy of the names, the cuspa with the cuspare. The latter not only vegetates in the missions of the Rio Carony, but also to the west of Cumana, in the gulf of Santa Fe. It furnishes the druggists of Europe with the famous Cortex Angosturae, and forms the genus Bonplandia, described by M. Willdenouw in the Memoirs of the Academy of Berlin, from notes communicated to him by us.
It is singular that, during our long abode on the coast of Cumana and the Caracas, on the banks of the Apure, the Orinoco, and the Rio Negro, in an extent of country comprising forty thousand square leagues, we never met with one of those numerous species of cinchona, or exostema, which are peculiar to the low and warm regions of the tropics, especially to the archipelago of the West India Islands. Yet we are far from affirming, that, throughout the whole of the eastern part of South America, from Porto Bello to Cayenne, or from the equator to the 10th degree of north latitude between the meridians of 54 and 71 degrees, the cinchona absolutely does not exist. How can we be expected to know completely the flora of so vast an extent of country? But, when we recollect, that even in Mexico no species of the genera cinchona and exostema has been discovered, either in the central table-land or in the plains, we are led to believe, that the mountainous islands of the West Indies and the Cordillera of the Andes have peculiar floras; and that they possess particular species of vegetation, which have neither passed from the islands to the continent, nor from South America to the coasts of New Spain.