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been without utility. Obliged during my residence at Acapulco to pass several nights in the open air for the purpose of making astronomical observations, I constantly felt for two or three hours before sun-rise, when the temperature of the sea was very different from that of the Continent, a small current of air which entered by the breach of San Nicolas. This current is the more salutary, as the atmosphere of Acapulco is poisoned by the miasmata which exhale from a marsh called the cienega del castillo, situated to the east of the town. The stagnant water of this marsh disappears every year, which occasions the death of an innumerable quantity of small thoracic fishes, of a mucilaginous skin, which the Indians designate by the name of popoyote or awolotl", although the true arolotl of the lakes of Mexico (Siren pisciformis of Shaw) differs essentially from it, and is only, according to M. Cuvier, the larva of a great salamander. These fishes, which by rotting in heaps diffuse emanations through the neighbouring air, are justly considered the principal cause of the putrid bilious fevers which prevail on that coast. Between the town and the cienega, there are lime fur
* The axolotl of Acapulco has nothing in common with that of the valley of Mexico but its colour. It is a scaly fish with two dorsal fins, of an olive brown, speckled with small yellow and blue spots.
naces in which great masses of sea-weed are calcinated. Notwithstanding the specious theories of M. Mitchell " on the oxide of azote, Acapulco is one of the most unhealthy places of the New Continent. Perhaps even if this port, instead of being frequented with vessels from Manilla, Guayaquil, and other places situated under the torrid zone, were to receive vessels from Chili and the north-west coast of America, and if the town were visited at the same time by a greater number of Europeans, or inhabitants of the central table land, the bilious fevers would soon degenerate into yellow fever, and the germ of that malady would develope itself at Acapulco in a still more fatal manner than at Vera Cruz. w On the east coast of Mexico, the north winds cool the air so that the thermometer falls to 17° centegrade *, and at the end of the month of February, I have seen it remain for whole days under 21°f ; while during the same period, the air being calm, at Acapulca it islat?8° or 30°. f The latitude of Acapulco is 8° farther south than that of Vera Cruz: and the high Cordilleras of Mexico shelter it from the currents of cold air which rush in from Canada upon the coast of Tabasco. The temperature of the air remains there in summer during the day almost continually between 30° and 86° of the centigrade thermometer. S I have observed that on all the coasts, the
* According to this author, the oxide of azote, considered as the cause of the malignant and intermittent fevers, is absorbed by the lime, and for that reason the healthiest parts of England, France, and Sicily, are calcareous (American Medical Repos. vol. ii. p. 46.) The influence of rocks on the great ačrial ocean, puts us in mind of the dreams of the Abbé Giraud Soulavie, according to whom “ the basalts and amygdaloids augment the electrical charge “ of the atmosphere, and have an influence on the morals “ of the inhabitants, rendering them light-headed, revo“lutionary, and inclined to abandon the religion of their “‘ancestors.” Whatever idea may be formed of the miasmata which occasion the insalubrity of the air, it appears very improbable, according to the present state of our chemical knowledge, that ternary or quarternary combinations of phosphorus, hydrogen, azote, and sulphur, can be absorbed by lime, and particularly by the carbonate of lime. Such, however, has been the political influence of the theories of M. Mitchell, in a country where the wisdom of the magistrates is very justly admired, that while I was at quarantine in the Delaware, on arriving from the West Indies at Philadelphia, I saw officers of the committee of health, gravely cause the opening of the hatchway to be painted with water of lime, that the septon or miasma of the yellow fever of the Havannah, which they supposed to exist in our vessel, should fix itself on a band of lime of three decimetres (about a foot) in breadth. Was it at all surprising that our Spanish sailors thought there was something magical in this pretended means of disinfection ?
* 62° of Fahrenheit. Trans. T 69°8' of Fahrenheit. Trans. # 82° and 86° 1' Fahrenheit. Trans. § Between 86° and 96° 8' of Fahr. Trans.
temperature of the sea has a great influence on that of the neighbouring continent. Now the heat of the sea not only varies according to the latitude, but also according to the number of shallows, and the rapidity of the currents which flow from different climates. On the coast of Peru, under the 8° and 12° of south latitude, I found the temperature of the South Sea at its surface, from 15° to 16° centigrades"; while out of the current which sets in strongly from the straits of Magellan towards Cape Pariña, the great equinoctial ocean is at a temperature of from 25° to 26°. Thus the thermometer fell at Lima in the months of July and August, 1801, to 18° 5'f, and oranges will hardly grow
there. I observed also that the heat of the sea
in February 1804, at the port of Vera Cruz, was only from 20° to 22° S, while at the shore of
Acapulco I found it in March 1803, from 28° to 29°. || The union of all these circumstances increases the heat of the climate on the western coast. The heats are less interrupted at Acapulco than at Vera Cruz, and we may believe, if ever the yellow fever begins to prevail in
| From 82° 4' to 84° 2' of Fahr. Trans. See my Recueil d'Observations Astronomiques, t. i. p. 317. (m. 256 and 559).
the former of these ports, that it will continue during the whole year, as in the island of Trinidad, at Saint Lucia, and Guayra, and wherever the mean temperatures of the different months only vary from 2° to 8°." In the low regions of Mexico, as well as in Europe, the sudden suppression of transpiration, is one of the principal occasional causes of the gastric or bilious fevers, especially of the cholera morbus which is announced by such frightful symptoms. The climate of Acapulco, of which the temperature is uniform throughout the different parts of the year, gives rise to those suppressions of transpiration, from the extraordinary coolness which prevails a few hours before sun-rise. On that coast those persons who are not seasoned to the climate run the greatest risks when they travel by night with light clothing, or sleep in the open air. At Cumana, and in other parts of equinoctial America, the temperature of the air only diminishes towards sun-rise 1° or 2° centigrade; by day the
* From 3° 6' to 5° 4’ of Fahr. Trans. The differences of mean temperature between the hottest and coldest months, are, in Sweden, under the 63° 50' of latitude, 28° 5'; in Germany, under the 50° 5' of latitude, 23°2'; in France, under the 48° 50' of latitude, 21° 4'; in Italy, under the 41° 54" of latitude, 20° 6’; and in South America, under the 10° 27' of latitude, 2°7'. See my comparative tables in the additions to Thomson's Chemistry, (Translation of M. Riañult) t. i. p. 106.