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moist and easterly winds are dry, while in North America northeasterly are cold and humid and northwesterly winds cold and dry.
MISCELLANEOUS. Hot WINDS OF DESERTS.-On the deserts of Africa and Arabia there sometimes prevails a wind extremely dry and intensely hot, which raises clouds of sand and transports it to a great distance. This wind is known in the desert of Africa and Western Asia as Simoon or Simoun (from the Arabic samma, signifying hot, poisonous, or anything disagreeable or dangerous), while in Egypt it is called Khamsin (Arabic for fifty), because it generally blows for 50 days, from the end of April to the time of the inundation of the Nile. This hot, dusty wind is felt in neighboring regions where it is known under different names. In Sicily, South Italy, and adjoining districts it is called the Sirocco. This wind is the plague of the Two Sicilies, and sometimes extends to the shores of the Black and Caspian Seas and to the steppes beyond the Volga. It is called the Samiel in Turkey, from its reputed poisonous qualities. The Solano of Spain is a southeast wind, which prevails at certain seasons in the plains of Mancha and Andalusia, particularly at Seville and Cadiz. This wind produces dizziness and heats the blood to an unusual degree. The Harmattan of Guinea and Senegambia belongs to the same class of winds. It is a periodical wind, blowing from the dry desert of Africa to the Atlantic, from latitude 15° north to latitude 1° south, during December, January, and February. It may be said of all these winds that their destructive effects on animal and vegetable life are due rather to their parching dryness, glowheat, and choking dust than to any really poisonous qualities.
PECULIARITIES OF WINDS FROM MOUNTAINS.—The winds proceeding from mountains present many interesting phases, a few of which will be described. The Pampero is a wind which blows chiefly in the summer season from the Andes, across the pampas of Buenos Ayres to the sea coast. It is thus a northwest wind, or part of the anti-trade of the southern hemisphere. It is a dry wind, frequently darkening the sky with clouds of dust, drying up the vegetation of the pampas, and often extending to a considerable distance seaward. Some competent authorities assert that the dust which is brought to the shores of Southern Europe comes not from Africa but from South America. They arrived at this conclusion by making microscopic examinations of the sand or dust, in which were found certain organisms and dried infusoria which are known to exist only in South America.
This theory further states that the dust was elevated into the upper regions of the atmosphere, where it met a current from the southwest and was transported over 5,000 miles before it again fell to the earth.
Puna WINDS.—To the eastward of Arequipa, in Peru, there is a barren table-land, between two great chains of the Andes, called the Puna or the Punos, which, for four months of the year is swept by cold, dry winds. These winds are part of the south trade-winds, which, after having crossed the lofty range of the Cordilleras, are cooled and parched to a degree that has perhaps no parallel in any other country in the world. The inhabitants, in traveling, find it necessary to protect their faces from the glare and heat of the day and from the intense cold of the night. The drying qualities of the Puna wind are so excessive that the bodies of dead animals exposed to it are very soon turned into mummies. Prescott states that it was in this district that the ancient inhabitants of Peru preserved their dead.
In the south of Europe north winds are notorious for their violence. The great differences of the temperature of the Alps, the Mediterranean, and Africa, explain them; and when the polar current, with high atmospheric pressure generally accompanying it, is descending at the same time over Europe, the effect is greatly heightened.
Of these winds the most noted is the Bora. This word seems to be a corruption of Boreas, though said to be derived from a Sclavonic term for "furious tempest.' The Bora is greatly dreaded in the upper part of the Gulf of Venice, where it rushes down from the whole line of the Julian Alps with such irresistible fury that not only numbers of vessels are sacrificed but it ravages the shore also, being feared as much for the suddenness of its attack as for its violence. Entire districts are rendered nearly uninhabitable by the destructive effects of this wind on all vegetation. Its general direction is between north and northeast, and its most usual continuance about fifteen or twenty hours, with heavy_squalls and terrible thunder, lightning, and rain at intervals. But the Bora most feared, and with justice, is that which blows in sudden gusts for three days, subsides, and then resumes its former force for three days more.
The Mistral (maestral) is the term applied by the country people to the northwest wind which sweeps from France down on the Gulf of Lyons. This wind is experienced in both summer and winter, though it is more violent and of longer duration in the latter season. In summer the mistral usually blows dur
ing clear weather and seldom lasts more than twenty-four hours, while in winter it often lasts for several days and is accompanied by heavy rains. As a rule this wind blows hardest during the day, decreasing toward sunset, showing the direct effect of change of temperature in producing wind; for, during the day, the difference of temperature between the cold air of the mountains and the warm air over the sea is much greater than at night. These same winds prevail in the Gulf of Genoa and with equal strength, only that here, from the trend of the coast, they become N. N. E. in the middle of the Gulf.
The terrific squalls experienced in the Straits of Magellan, called by the natives Williwaws, undoubtedly owe their suddenness and violence to the great height of the mountains in that region (which are covered with ice and snow all the year) and tri the corresponding differences of temperature of the air at such great elevations and that at the surface of the water.
PRACTICAL NOTES ON REVOLVING STORMS. It is now generally conceded by all who have had opportunity for personal observation, and who have given sufficient attention to the subject of Ocean Storms, that the most severe gales met with at sea are what is commonly known as Revolving Storms, variously called by seamen HURRICANES, TYPHOONS, CYCLONES, &c., according to the locality in which they blow.
The distinctive characteristics of these storms are sufficiently marked to distinguish them from the ordinary straight-line gales that blow; and the following brief practical remarks are intended to assist and enable the Navigator who may not be familiar with the subject of revolving storms, to not only judge of the character of the coming gale, but also to take timely measures to avoid the dangerous part of it, either by heaving-to on the proper tack or by running away from it, as the case may be; and also, in particular cases where the track of the storm lies in the same direction as the ship's course, to take advantage of it and run along with it.
In the year 1831 Mr. William Redfield, of New York, after long and careful personal investigation and study of the subject, published a paper, in which he demonstrated that the gales on the American coast were whirlwinds and had a progressive or forward movement, traveling on curved tracks at a considerable rate, and were traceable from the West Indies along the coast of the United States, curving off to the eastward at some point between the Bermudas and the banks of Newfoundland.
Professor Doyé. of Berlin, after investigating a number of heavy gales that had attracted the attention of scientific men in Germany about the same time, came to similar conclusions regarding the character of those gales.
In 1838 Lieutenant-Colonel Reid, of the Royal Engineers, published a valuable work on the law of storms, in which he agreed in all particulars with the views of Mr. Redfield, having verified by personal observation all his theory. From investigations of storms in the South Indian Ocean, Colonel Reid further proved that the storms in the southern hemisphere revolve in the opposite direction to those in the northern hemisphere.
THEORY OF STORMS.-Upon the above standard authorities, and upon the recorded experience of a great many seamen whose reports are confirmatory of the Redfield theory, is based the assumption that the currents of air within the limits of the storm disc move in concentric circles around a center of low pressure, or, in other words, that the direction of the wind at any point within the storm disc is tangent to a circle the center of which is the storm center, and lies 90° (eight points) to the right, or on the right hand in the northern hemisphere, and 90° (eight points) to the left, or on the left hand in the southern hemisphere, supposing the observer to be facing the winds, as will appear by inspection of the accompanying storm cards.
EXCEPTIONS TO THE THEORY.—It is not pretended here to assert that this theory is absolutely true, or that the rule has no exception. To the contrary, the same experience that proves the theory also goes to show that the winds within the storm disc may, from various causes, be diverted from the circular course to any direction between the tangent and the radius of the circle, toward the center.
ist. Proximity of Land.—The proximity of land may generally be expected to affect the course of the winds in that part of the storm disc either in contact with it or under the influence of it, and may also, if the course of the storm is such as to strike a high coast at a considerable angle, so distort the entire storm disc as to render it difficult to determine the locality of the center from the direction of the wind; but if it be remembered that the effect of land upon a storm will always be to flatten it in, and thus bring the center nearer to the shore than the direction of the wind according to the circular theory would indicate, the Navigator may, even in such a case, by taking into account the character of the land and its distance from the
place of the ship, estimate sufficiently near the position of the center to take proper measures for avoiding it.
2d. Local Disturbances.—Temporarily, from local disturbances within the storm disc, for a full discussion of which the Navigator is referred to the standard works on storms, viz. : Piddington's Sailors' Hornbook, Reid on the Law of Storms, Dove's Law of Storms, &c.
STORM PROBLEM.-The storm problem, considered only in its relation to the safe navigation of a ship at sea, is very simple, and may be briefly summed up under the following heads, which contain all that is necessary for a practical solution of it:
Ist. Ascertain the character of the storm and locate the center.
2d. Determine the position of the ship in the storm disc, or the semicircle of the storm in which the ship is situated.
3d. Ascertain approximately the direction in which the storm is moving.
4th. Decide what to do with the ship to escape the center, or take advantage of the fair winds, as the case may be.
To ascertain the character of the storm, consult the barometer and the general appearance of the weather.
First.—The barometer generally indicates the approach of a storm by a restless oscillating motion of the mercury, caused by a disturbed condition of the atmosphere in the vicinity of a storm, and the consequent passage over it of atmospheric waves of different heights. These oscillations have been observed to vary from a just perceptible motion to 0.02 in.
Second.—The barometer often rises suddenly just on the border in front of a storm, by reason of the air banking up there, and therefore, if the clouds and general appearance of the weather indicate the approach of a storm, the rise in the barometer, if any occurs, is no guarantee that it will not come, but rather a sign that a severe storm is coming. (The barometer will probably not rise much in front of a slowly moving storm.)
Third.—A very rapid fall of the barometer after fairly entering the storm disc may be regarded as evidence of a very violent