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and 2d degree of north latitude. The extent of the south-east trade is not precisely ascertained, but it probably ranges from the 10th to the 21st degree of south latitude. In the Atlantic, the former is comprised be tween the 30th and 8th degrees of north latitude, and the latter within the limits of the 3d degree of north and the 28th degree of south latitude.

94. The limits, however, are not stationary, but are dependent upon the season-advancing towards the north during the summer of the northern hemisphere, and receding to the south as the sun withdraws to the southern tropic. Thus, on the west coast of Europe, the north-east trade has been found to extend as far as Madeira, and even to Mafra, in Portugal.

This

95. CALMS. In the vicinity of the Cape Verde isles, between the 8th and 3d degree of north latitude, is a tract denominated by mariners the rainy sea. region is doomed to continual calms, broken up only by terrific storms of thunder and lightning, accompanied by torrents of rain. A suffocating heat prevails, and the torpid atmosphere is disturbed, at intervals, by short and sudden gusts, of little extent and power, which blow from every quarter of the heavens, in the space of an hour-each dying away ere it is succeeded by another. In these latitudes, vessels have sometimes been detained for weeks.

In the Pacific, the region of calms is comprised within the 2d degree of north and south latitude, near Cape Francis and the Galapagos islands—a narrow belt of ocean separating the two trades. Here, likewise, dreadful tempests prevail.

96. According to Humboldt, a similar state of the atmosphere exists, during the months of February and March, on the western coast of Mexico, between the 13th and 15th degrees of north latitude, and 103d and 106th degrees of west longitude. A ship, richly laden with cocoa, was here becalmed for the space of twenty

Are the limits stationary? Upon what do they depend?
Give examples. Where is the rainy sea? Describe it.
Where are the calms in the Pacific? What instance is given?

eight days, when the water failing, the crew were compelled by their sufferings to abandon the vessel and seek the shore, eighty leagues distant, in an open boat.

97. The calms are supposed to be caused in the following manner. The adjacent continents to the east of these stagnant regions being far more intensely heated than the sea, the air over the latter would rush easterly towards the land, were it not arrested by a contrary impulse in the direction of the trade wind. If these opposing forces are at any time equally strong, the atmosphere is motionless, and a dead calm ensuesjust as a vessel, in ascending a stream, continues stationary when the power of the wind is exactly balanced by that of the current. When, however, the relative strength of these forces rapidly changes, those short and sudden gusts which have been noticed will arise, as one or the other of these impulses prevails.

98. The presence of a highly heated region is strikingly marked in the case of the rainy sea. To the east lies the great African desert, from whose burning surface a vast volume of hot and rarefied air is perpetually rising.

Another cause must not be forgotten, which applies, more particularly, to the calms near Cape Francis. This tract is directly under the equator, and from its peculiar situation, the upward current of rarefied air is probably here so strong as to neutralize the action of the trade winds.

The limits of the calms vary also with the seasons. Thus, in the Atlantic, the range in August is between 3° 15′ and 13° N. Lat., but in February, extends from 1° 15' to 6° N. Lat.

WINDS OF THE HIGHER LATITUDES.

99. The upper equatorial currents, flowing off towards either pole, descend, on their passage, to the earth, and since they carry with them an excess of easterly velocity, will become, upon the principles already

How do the calms originate? What are their limits?
What is the direction of the wind in the higher latitudes?

explained, (Art. 89,) south-westerly winds, in the northern hemisphere, and north-westerly in the southern.

Such would be the course of these currents if left to themselves; but as they meet on their passage with counteracting winds, and are influenced by a variety of causes, their direction is more or less changed; yet not so much, but that a marked predominance in the frequency of westerly winds exists in both hemispheres. 100. That this is true, in regard to the northern hem

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* Kaemtz_remarks of Russia, "that the number of observations have not been sufficient to enable us to deduce any thing conclusive."

What gives them this direction?

Explain fig. 6., and give the course of the wind for the several countries.

isphere, is obvious from the annexed cut, figure 6., which presents the results of a multitude of observations. A quarter of the circumference of a circle is here supposed to be divided into ninety parts, called degrees, and the inclination of the several lines on which the arrows are placed, to the north and south line, measures, in degrees, the average or mean course of the wind, in the several places mentioned.

The degrees are reckoned from the south, in all cases except Russia, where they are counted from the north. The points of the arrows indicate the quarter towards which the wind blows.

101. The prevalence of westerly winds in the high latitudes of the north is also shown by the fact, that the average length of the outward passage, by packet, from New York to Liverpool, is but twenty-three days, while that of the return voyage is forty. It also appears, from the observations of Hamilton, during twenty-six voyages between Philadelphia and Liverpool, extending from 1798 to 1817, that, out of 2029 days on which the wind blew, it came from the west 1101; a result agreeing with the observations of McCord, at Montreal, who found that, from 1836 to 1840, inclusive, the westerly winds at this station constituted more than one-half of all the winds that blew. bearing the ratio of 54 to 100.

102. In the high southern latitudes, the same fact has been observed. Lieut. Maury remarks, that at Cape Horn there are three times as many westerly as easterly winds, and that he has seen vessels arrive at Valparaiso and Callao, after having been detained off the Cape, by gales and head winds, for the space of eighty, and even one hundred and twenty days. In the late Exploring Expedition, the ship Vincennes remained at Orange Harbor, in Terra del Fuego, for the space of sixty days, during which time the weather was exceeding variable; for thirteen days the wind blew from the north, eastward, and south-east, while for forty-seven, it prevailed from the west.

State facts respecting westerly winds in the high northern latitudes.
The same in regard to the high southern latitudes.

UPPER WESTERLY WIND OF THE TROPICS.

103. The prevalence of a westerly wind, above the trades, within the torrid zone, is shown by many conclusive facts. In 1812, ashes from the volcano of St. Vincents were carried easterly, falling upon the island. of Barbadoes; and the captain of a Bristol ship declared, that at this time volcanic dust descended to the depth of five inches, upon the deck of his vessel, at the distance of five hundred miles to the east of the former island.

In 1835, an eruption occurred of the volcano of Con sanguina, situated in Guatimala. The height of the crater is 3800 feet, and from it issued clouds of ashes, which obscured the sun for five days, and being borne along in a north-easterly direction, by the upper current, fell in the streets of Kingston, Jamaica, seven hundred and thirty miles distant. Even in the latitude of Teneriffe, nearly all travelers have found a westerly wind at the summit of the peak, while the regular trade was blowing in a contrary direction, at the level of the

ocean.

PERIODICAL WINDS.

104. MONSOONS. In certain countries within and near the tropics, the regular action of the trade wind is destroyed by the monsoons, which are periodical gales, deriving their name from the Malay word moussin, signifying seasons. These winds blow, from a certain quarter, for one half of the year, and during the other half from an opposite point; and at the time of their shifting, dead calms, tempests, and variable winds alter nately occur.

105. From April to October, the south-west monsoon prevails north of the equator, and the south-east in the southern hemisphere; but from October to April, the north-west monsoon blows south of the equator, and the north-east in the northern hemisphere.

What is the direction of the wind above the trades? Give the proofs. What are the monsoons? In what manner do they blow?

From April to October what monsoons prevail, and where?

From October to April what monsoons prevail, and where?

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