Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1

by Alexander von Humboldt; Aimé Bonpland

I have published in another work* (* Nouvelle Espagne tome 2.) the observations made by M. Bonpland and myself on the locality of the towns periodically subject to the visitation of yellow fever; and I shall not hazard here any new conjectures on the changes observed in the pathogenic constitution of particular localities. The more I reflect on this subject, the more mysterious appears to me all that relates to those gaseous emanations which we call so vaguely the seeds of contagion, and which are supposed to be developed by a corrupted air, destroyed by cold, conveyed from place to place in garments, and attached to the walls of houses. How can we explain why, for the space of eighteen years prior to 1794, there was not a single instance of the vomito at Vera Cruz, though the concourse of unacclimated Europeans and of Mexicans from the interior, was very considerable; though sailors indulged in the same excesses with which they are still reproached; and though the town was not so clean as it has been since the year 1800?

The following is the series of pathological facts, considered in their simplest point of view. When a great number of persons, born in a cold climate, arrive at the same period in a port of the torrid zone, not particularly dreaded by navigators, the typhus of America begins to appear. Those persons have not had typhus during their passage; it appears among them only after they have landed. Is the atmospheric constitution changed? or is it that a new form of disease develops itself among individuals whose susceptibility is highly increased?

The typhus soon begins to extend its ravages among other Europeans, born in more southern countries. If propagated by contagion, it seems surprising that in the towns of the equinoctial continent it does not attach itself to certain streets; and that immediate contact* does not augment the danger, any more than seclusion diminishes it. (* In the oriental plague (another form of typhus characterised by great disorder of the lymphatic system) immediate contact is less to be feared than is generally thought. Larrey maintains that the tumified glands may be touched or cauterized without danger; but he thinks we ought not to risk putting on the clothes of persons attacked with the plague.—Memoire sur les Maladies de l'Armee Francoise en Egypte page 35.) The sick, when removed to the inland country, and especially to cooler and more elevated spots, to Xalapa, for instance, do not communicate typhus to the inhabitants of those places, either because the disease is not contagious in its nature, or because the predisposing causes are not the same as in the regions of the shore. When there is a considerable lowering of the temperature, the epidemic usually ceases, even on the spot where it first appeared. It again breaks out at the approach of the hot season, and sometimes long before; though during several months there may have been no sick person in the harbour, and no ship may have entered it.

The typhus of America appears to be confined to the shore, either because persons who bring the disease disembark there, and goods supposed to be impregnated with deleterious miasms are there accumulated; or because on the sea-side gaseous emanations of a particular nature are formed. The aspect of the places subject to the ravages of typhus seems often to exclude all idea of a local or endemical origin. It has been known to prevail in the Canaries, the Bermudas, and among the small West India Islands, in dry places formerly distinguished for the great salubrity of their climate. Examples of the propagation of the yellow fever in the inland parts of the torrid zone appear very doubtful: that malady may have been confounded with remitting bilious fevers. With respect to the temperate zone, in which the contagious character of the American typhus is more decided, the disease has unquestionably spread far from the shore, even into very elevated places, exposed to cool and dry winds, as in Spain at Medina-Sidonia, at Carlotta, and in the city of Murcia. That variety of phenomena which the same epidemic exhibits, according to the difference of climate, the union of predisposing causes, its shorter or longer duration, and the degree of its exacerbation, should render us extremely circumspect in tracing the secret causes of the American typhus. M. Bailly, who, at the time of the violent epidemics in 1802 and 1803, was chief physician to the colony of St. Domingo, and who studied that disease in the island of Cuba, the United States, and Spain, is of opinion that the typhus is very often, but not always, contagious.

Since the yellow fever has made such ravages in La Guayra, exaggerated accounts have been given of the uncleanliness in that little town as well as of Vera Cruz, and of the quays or wharfs of Philadelphia. In a place where the soil is extremely dry, destitute of vegetation, and where scarcely a few drops of water fall in the course of seven or eight months, the causes that produce what are called miasms, cannot be of very frequent occurrence. La Guayra appeared to me in general to be tolerably clean, with the exception of the quarter of the slaughter-houses. The sea-side has no beach on which the remains of fuci or molluscs are heaped up; but the neighbouring coast, which stretches eastward towards Cape Codera, and consequently to the windward of La Guayra, is extremely unhealthy. Intermitting, putrid, and bilious fevers often prevail at Macuto and at Caravalleda; and when from time to time the breeze is interrupted by a westerly wind, the little bay of Cotia sends air loaded with putrid emanations towards the coast of La Guayra, notwithstanding the rampart opposed by Cabo Blanco.

The irritability of the organs being so different in the people of the north and those of the south, it cannot be doubted, that with greater freedom of commerce, and more frequent and intimate communication between countries situated in different climates, the yellow fever will extend its ravages in the New World. It is even probable that the concurrence of so many exciting causes, and their action on individuals so differently organized, may give birth to new forms of disease and new deviations of the vital powers. This is one of the evils that inevitably attend rising civilization.

The yellow fever and the black vomit cease periodically at the Havannah and Vera Cruz, when the north winds bring the cold air of Canada towards the gulf of Mexico. But from the extreme equality of temperature which characterizes the climates of Porto Cabello, La Guayra, New Barcelona, and Cumana, it may be feared that the typhus will there become permanent, whenever, from a great influx of strangers, it has acquired a high degree of exacerbation.

Tracing the granitic coast of La Guayra westward, we find between that port (which is in fact but an ill-sheltered roadstead) and that of Porto Cabello, several indentations of the land, furnishing excellent anchorage for ships. Such are the small bay of Catia, Los Arecifes, Puerto-la-Cruz, Choroni, Sienega de Ocumare, Turiamo, Burburata, and Patanebo. All these ports, with the exception of that of Burburata, from which mules are exported to Jamaica, are now frequented only by small coasting vessels, which are there laden with provisions and cacao from the surrounding plantations. The inhabitants of Caracas are desirous to avail themselves of the anchorage of Catia, to the west of Cabo Blanco. M. Bonpland and myself examined that point of the coast during our second abode at La Guayra. A ravine, called the Quebrada de Tipe, descends from the table-land of Caracas towards Catia. A plan has long been in contemplation for making a cart-road through this ravine and abandoning the old road to La Guayra, which resembles the passage over St. Gothard. According to this plan, the port of Catia, equally large and secure, would supersede that of La Guayra. Unfortunately, however, all that shore, to leeward of Cabo Blanco, abounds with mangroves, and is extremely unhealthy. I ascended to the summit of the promontory, which forms Cabo Blanco, in order to observe the passage of the sun over the meridian. I wished to compare in the morning the altitudes taken with an artificial horizon and those taken with the horizon of the sea; to verify the apparent depression of the latter, by the barometrical measurement of the hill. By this method, hitherto very little employed, on reducing the heights of the sun to the same time, a reflecting instrument may be used like an instrument furnished with a level. I found the latitude of the cape to be 10 degrees 36 minutes 45 seconds; I could only make use of the angles which gave the image of the sun reflected on a plane glass; the horizon of the sea was very misty, and the windings of the coast prevented me from taking the height of the sun on that horizon.

The environs of Cabo Blanco are not uninteresting for the study of rocks. The gneiss here passes into the state of mica-slate (Glimmerschiefer.), and contains, along the sea-coast, layers of schistose chlorite. (Chloritschiefer.) In this latter I found garnets and magnetical sand. On the road to Catia we see the chloritic schist passing into hornblende schist. (Hornblendschiefer.) All these formations are found together in the primitive mountains of the old world, especially in the north of Europe. The sea at the foot of Cabo Blanco throws up on the beach rolled fragments of a rock, which is a granular mixture of hornblende and lamellar feldspar. It is what is rather vaguely called PRIMITIVE GRUNSTEIN. In it we can recognize traces of quartz and pyrites. Submarine rocks probably exist near the coast, which furnish these very hard masses. I have compared them in my journal to the PATERLESTEIN of Fichtelberg, in Franconia, which is also a diabase, but so fusible, that glass buttons are made of it, which are employed in the slave-trade on the coast of Guinea. I believed at first, according to the analogy of the phenomena furnished by the mountains of Franconia, that the presence of these hornblende masses with crystals of common (uncompact) feldspar indicated the proximity of transition rocks; but in the high valley of Caracas, near Antimano, balls of the same diabase fill a vein crossing the mica-slate. On the western declivity of the hill of Cabo Blanco, the gneiss is covered with a formation of sandstone, or conglomerate, extremely recent. This sandstone combines angular fragments of gneiss, quartz, and chlorite, magnetical sand, madrepores, and petrified bivalve shells. Is this formation of the same date as that of Punta Araya and Cumana?

Scarcely any part of the coast has so burning a climate as the environs of Cabo Blanco. We suffered much from the heat, augmented by the reverberation of a barren and dusty soil; but without feeling any bad consequences from the effects of insolation. The powerful action of the sun on the cerebral functions is extremely dreaded at La Guayra, especially at the period when the yellow fever begins to be felt. Being one day on the terrace of the house, observing at noon the difference of the thermometer in the sun and in the shade, a man approached me holding in his hand a potion, which he conjured me to swallow. He was a physician, who from his window, had observed me bareheaded, and exposed to the rays of the sun. He assured me, that, being a native of a very northern climate, I should infallibly, after the imprudence I had committed, be attacked with the yellow fever that very evening, if I refused to take the remedy against it. I was not alarmed by this prediction, however serious, believing myself to have been long acclimated; but I could not resist yielding to entreaties, prompted by such benevolent feelings. I swallowed the dose; and the physician doubtless counted me among the number of those he had saved.