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naces in which great massesi 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,

* 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. I. p. 46.). The influence of rocks on the great aërial 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«6 lutionary, and inclined to abandon the religion of their «. ancestors." Whatever idea may be formed of the miasnata 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 mar gistrates is very justly, admired, that while I was.at quaran. tine 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 alt surprising that our Spanish sailors thought there was something magical in this pretended means of disinfection ?

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.is „. 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° t; while during the same period, the air being calm, at Acapulco it is at 28° or 30° 1. The latitude of Acapulco is 3* 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 36° of the centigrade thermometer §.

I have observed that on all the coasts, the

* 62° of Fahrenheit. Trans.
+ 69o. 8 of Fahrenheit. Trans. ..

82o and 86'. 1' Fahrenheit. Trans. i
Between 86° and 96o. 8 of Fahr. Transa

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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 go 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 264. Thus the thermometer fell at Lima in the months of July and August, 1801, to 13° 5' 1 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 200 to 22° §, while at the shore of Acapulco I found it in March 1803, from 28° to 29° 11. 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,

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if ever the yellow fever begins to prevail in 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 3°*.

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 30. 6 to 5o. 4 of Fahr. Trans. The differences of mean temperature between the hottest and coldest months, are in Sweden, under the 63° 50' of latitude, 28o. 5; in Germany, under the 500.51 of latitude, 230. 2 ; in France, under the 48° 50 of latitude, 21°. 4; in Italy, under the 410 64.1 of latitude, 20°. 6; and in South America, under the 10° 27' of latitude 20.7. See my comparative tables in the additions to Thomson's Chemistry, (Translation of M. Riffault) T. i. p. 106.

thermometer is at 28° or 299, and by night at 23° or 24°; but at Acapulco I found the heat of the air by day 29° or 30°, during the night it kept at 26', and from three o'clock in the moming, to sun-rise it suddenly fell to 17° or 18o. This change makes the strongest impression on the organs. No where under the tropics did I ever feel so great a cooless during

the latter half of the night. It was like passing (suddenly from summer to autumn; and the sun was hardly risen when we began again to complain of the heat. In a climate where the health principally depends on the functions of the skin, and where the orgáns are affected with the smallest changes of temperature* a cooling of the air to the extent of 10° or 12° occasions suppression of transpiration very dangerous to Europeans not seasoned to the climate.

It has been falsely affirmed that the vomito never prevailed in any part of the southern hemisphere, and the cause of this phenomenon has been attributed to the cold believed to be

* The temperature of the air at Guayaquil keeps so uniformly between 290 and 320 centigrades, that the inhabitants complain of cold when the thermometer suddenly falls to 23° or 24%. These phenomena are very remarkable in a physiological point of view; and they prove that the excitability of the organs is increased by the uniformity, and continued action of habitual stimulus.

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