not bar its passage and disturb its course at numerous points. The continental lands impede its march, and cut it, so to speak, into several pieces. The trade wind of the Pacific Ocean is arrested by Australia; that of the Indian Ocean by Africa; that of the Atlantic is stopped by America. We shall then rapidly examine the courses of the trade wind in each of these oceans; for it is essentially at the surface of the ocean, where it reigns supreme, that we can learn its true character.

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The trade wind of the Pacific begins to make itself felt at a certain distance from the western coasts of America, and blows almost without interruption as far as the 'oasts of Australia. The north-east current is regular oetween 2° and 25° north latitude, which may be considered as the southern and northern limits. But in the summer it rises a little further towards the north. was this constant and gentle wind that carried the first navigator, Magalhaens, whose ship made the voyage round the world, across this vast ocean, and that gave it the name of Pacific, which has been preserved to the present day. It is by this line still, that the Spanish galleons, laden with the gold of the New World, accomplished, during more than two centuries, their peaceful voyages from Acapulco to Manilla, sheltered at once. from the tempests and from the attacks of the nations envious of so much wealth. The south-east current is as regular south of the equator, but the limits are less known; it is found as far as the 21° of south latitude.

The region of calms is found in the space comprised between the 2° north latitude and the 2° south, between the two currents at their meeting. Here the ascending

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seems to neutralize the horizontal; the air is in a sort of factitious equilibrium, that the least accident violently disturbs. Thus, to a dead calm, succeed those sudden tempests, those violent squalls, those whirlwinds, those tornadoes, as the Spaniards call them, which are the terror of navigators. Thunder storms, accompanied by showers, are of almost daily occurrence.

The trade wind of the Atlantic is already modified by the position of this ocean lying between continents nearer to each other. It is, as it were, transported bodily several degrees towards the north. The northern limit of the north-east current is precisely fixed by the numerous navigators who traverse these seas; it commences between 28° and 30° north latitude. Its southern limit is about 8° north latitude. The region of calms occupies, on the average, the space comprised between the 3° and 8° of north latitude; but its position varies with the seasons; in August it extends from 3° to 13° north latitude; in February, from 1° to 6° north latitude. south-east current always blows, then, beyond the equator to the north.

The

Humboldt attributes, apparently with reason, this anomaly, on the one hand, to the direction of the coasts of South America, which favors the extension of the south-east trade wind, and of the warm waters of the great equatorial current towards the north; and, on the other, to the ooling influence of the high mountains of the continent, in the regions of the equator. The first of these causes tends to heat the sea of the Antilles; the second, to lower the temperature of the southern continent. The result of this difference must be to determine a cur

rent of air from the south, removing the limit of the north-east trade wind further north. The thermal equator, or the line of the greatest mean heat, passes, in fact, through the south of the sea of the Antilles.

The existence of the upper trade wind, coming from the west, or of the return trade wind, which has often. been doubted, seems to be proved in this ocean by two facts, often cited and very conclusive. The volcano of the island of St. Vincent, belonging to the lesser Antilles, in one of its eruptions hurled a column of volcanic cinders to a great height in the atmosphere; the inhabitants of the Barbadoes, situated east of St. Vincent, saw, with astonishment, the cinders falling in abundance upon their island. The 25th of February, 1835, the volcano of Cosiguina, in Guatemala, threw into the air such a quantity of cinders, that the light of the sun was darkened during five days; a few days after, they were seen to cover the streets of Kingston, in Jamaica, situated north-east of Guatemala. In these two cases it is evident that the cinders had reached the region of the upper trade wind, and had been carried by it from west to east, in the opposite direction to the lower trade wind. At the summit of the Peak of Teneriffe, most travellers have found a west wind, even when the north-east trade wind. prevailed on the seaboard.

The winds of the Indian Ocean experience still greater perturbations than those of the other two oceans of the tropics. If I have elsewhere called the Pacific the most oceanic of the oceans, the Atlantic the most maritime, I will call the Indian Ocean the most mediterranean. It

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