summer the winds are in the south, and in winter, in the north. The latter often blow with great violence in the Gulf of Mexico.

In Europe, we find similar relations. The mean direction of the wind in winter, in Paris, is S. 48° W.; in summer it is N. 88° W. _This result is confirmed in a great number of places in Europe. Schouw, in summing up all these observations, has established the following laws :

In winter, the direction of the wind is more southerly than during the rest of the year; in January its force attains its maximum.

In spring, east winds are common; at certain places in March; at others, in April. They diminish the force of the west current, which, in many countries, is at that time weaker than during the rest of the year. The relation of north to south winds is not constant, and varies according to the localities. In some, the direction is more northerly, in others more southerly, than the mean direction of the year.

In summer, especially in July, the winds blow chiefly from the west; their predominance over east winds attains its maximum; and, at the same time, the north winds become more common; whence it follows that the mean direction of the wind in this season is north of the annual mean.

In autumn, the predominance of west winds diminishes; those of the south more frequently blow, especially in October: so that, in many localities, the general direction is more southerly than in all the other months.

ON THE MODE OF THE PROPAGATION OF WINDS.

-Does a wind first blow in the country whence it comes, or in that whither it goes? Is an east wind, for example, first felt in the eastern countries, or in the western parts of Europe? This is a question that has often been agitated, without our having been able to resolve it in such a manner as will satisfy every individual case. I think that nothing positive can be said on this point; and I should be induced to believe that the wind commences in a point situated in the middle of the region which it occupies, and that it is thence propagated onward in each direction. The land and sea-breezes, the cause of which is well known, confirm what I have advanced. The sea-breeze is first felt on the coast; then, after some hours, in the interior of the land and in the open sea. It will follow, therefore, that an east wind will blow first in Germany, and a little later in Holland and Russia.

Since Franklin's time it has been generally admitted, that winds are rather felt in the countries towards which

they blow than in those whence they come. He quotes an observation favourable to this theory. One day, a strong N.E. wind arose about seven o'clock in the evening at Philadelphia, and prevented an eclipse of the moon from being observed. This gale was also felt at Boston, situated to the N.E. of Philadelphia, but not until eleven o'clock in the evening. A violent S.W. wind, which ravaged the United States, on the 12th of June, 1829, first blew at Albany, and then at New York, which is situated more to the south. However, there are numerous exceptions to this rule. The terrible hurricane from the S.W., on the 29th November, 1836, passed over London at ten o'clock in the morning; at the Hague, at one o'clock; at Amsterdam, at half-past one; at Embden, at four; at Hamburg, at six; at Lubeck, Bleckede, and Salzwedel, at seven o'clock; and finally, at Stettin, at half-past nine in the evening. It was, therefore, transported in the same direction as that in which it blew; and it took ten hours to traverse the space which separates London from Stettin; consequently, its velocity was 36 metres per second, or 12960 metres per hour.

PHYSICAL PROPERTIES OF CERTAIN WINDS.— When winds come from distant countries, they possess a part of the properties by which those countries are characterised. Thus, the west winds, that blow from the sea, are much more moist than the east, which traverse continents. The latter, particularly when they are N.E., are very cold, especially in spring; and they give rise to a great number of rheumatic affections. The very opposite sensations, produced by violent south or north winds, are much more marked in countries whose inhabitants live in the open air. I should not have mentioned these differences had not these winds been characterised by particular denominations. COLD WINDS.-In the south of Europe the north winds are celebrated for their violence and their severity. The opposition between the elevated temperature of the Mediterranean and the Alps covered with snow gives rise to aerial currents of extreme rapidity. If their effect is added to that of a general north wind, there is produced a north-east wind, having a violence of which we can form no idea. In Istria and Dalmatia this wind is known under the name of bora, and its force is such that it sometimes overturns horses and ploughs. It is the same up the valley of the Rhone, where a very cold south wind often prevails, which is named mistral, and which is not less formidable than the north wind, known in Spain under the name of gallego.

HOT WINDS.-Large deserts and plains covered with but

little vegetation engender very hot winds, which have given rise to marvellous stories, and still more extraordinary explanations. These winds prevail in the vast deserts of Asia and Africa, where we only find here and there a few oases of vegetation, in narrow valleys, where moisture may be preserved for some time. Nomade tribes travel over these deserts. Along the great rivers, such as the Nile, the Euphrates, and the Tigris, the earth is cultivated, and in those localities may be found commercial centres existing from the remotest antiquity, but which have no mutual communication, except by traversing the desert.

In all ages the Arab of the desert, a poor nomade, has detested the inhabitant of cities, who leads a comfortable and quiet life. Sometimes also he attacks cities to plunder them and lead the inhabitants into slavery, in order to sell them or to require a high ransom. Thus it is that Joseph was sold as a slave, and that the Jews, a nomade people, stole the precious vessels of the Egyptians, who, from the time of Moses, have not ceased to hate these wandering tribes. To the inhabitants of cities, the desert was the theatre of most exaggerated scenes of horror. Every marvellous tale of extraordinary adventures found in them credulous or prejudiced auditors; like as, in our days, the Turks form the most false and ridiculous ideas of Europe. The inhabitants of the desert did not care to eradicate these errors, for they constituted their strength; on the contrary, they supported them every time that they visited the cities. The merchants, who had traversed the desert, alone knew the truth; but they were in small numbers, made great profits in these voyages, and sought to frighten those who might be tempted to imitate them. Thus these opinions spread more and more among the multitude.

The Arabian writers are full of falsehoods on every thing relating to the desert. European travellers have even surpassed them. The Mahometan believes that he is performing a meritorious work in deceiving the infidel and closing to him the entrance to the desert. All those who have gone thither have profited well by these ridiculous stories, the exaggeration of which the Arabs themselves have confessed to them. L. Burckardt, of Bâle, is the first who has furnished us with positive information upon the phenomena of the desert, and especially on the winds that prevail there. He has thus reduced to their true value the fantastic accounts of his predecessors, Beauchamp, Bruce, and Niebuhr.

In Arabia, Persia, and the greater part of the countries

of the East, the burning wind of the desert is named samoun, simoum, sémoun, from the Arabic samma, which signifies at once hot and poisonous. It is also called samiel, from samm, poison. In Egypt it is called chamsin (fifty), because it blows for fifty days, from the end of April until June, at the commencement of the inundation of the Nile. In the western part of Sahara it is known under the_name of harmattan. The name samoun is most generally employed; but translators have always insisted on the meaning, poison, without reflecting that, like children, uncivilised people call every thing poison which is disagreeable or dangerous.

The dry soil of these countries becomes prodigiously heated, but without the heat penetrating deep, because the quartz sand, which covers them, is a bad conductor of heat: so that the thermometer is sometimes seen to attain 50° in the shade of a tent. If the wind rises it must be burning, and must transport sand and dust, which obscure the rays of the sun. The same occurs, if travellers may be believed, in the deserts of Nubia, on the coast of Guinea, and along Senegal. During a period of calm the ascending current of heated air is of itself sufficient to carry up the sand. Pottinger observed a phenomenon of this kind in the desert of Beloochistan. The surface of the soil there is uniformly covered with a fine sand, coloured red with iron, which, being the sport of the winds, forms undulated hills from three to six metres high. Towards mid-day these hills seemed to have disappeared, the sand was raised about three decimetres above the general level, and at each step we could fancy we were placing our foot on a plane raised three decimetres above the summit of these hills. This phenomenon was rarely evident in the evening and morning.

A strong wind raises a much more considerable quantity of sand; the troubled appearance of the horizon then announces the arrival of the samoun; afterwards the sky becomes obscured and the sun loses its brilliancy, paler than the moon, its light no longer projects a shadow; the green of the trees appears of a dirty blue, the birds are restless, and the affrighted animals wander in all directions.

The rapid evaporation occurring at the surface of the human body dries the skin, inflames the throat, accelerates respiration, and causes a violent thirst. The water contained in the skins evaporates, and the caravan is a prey to all the horrors of thirst. It is thus that, since the expedition of Cambyses, more than one caravan has perished in this desert; but we must class among Arab tales those histories of pestilential winds the contact of which causes death, and

which, like a cannon-ball, traverse a troop and choose out their victims. When the Arabs cover their face it is that the sand may not penetrate either into the eyes or into the mouth. For the same reason it is that camels turn their head from the side opposed to the wind; they never perform this manœuvre unless sand is in the air. "In June, 1813," says Burckardt, "in going from Siout to Esné, I was surprised by the samoun in the plain which separates Farschiout from Berdys. When the wind arose I was alone, mounted on my dromedary, and at a distance from every tree and habitation. I endeavoured to protect my face by wrapping it in a handkerchief. Meanwhile, the dromedary, into whose eyes the wind drove the sand, became restless, commenced galloping, and caused me to lose the stirrups. I remained lying on the earth without moving from the spot, for I could not see to a distance of ten metres, and I wrapped myself up in my clothes until the wind had abated. I then went to search after my dromedary, which I found at a very great distance, lying down near a bush that protected his head against the sand raised by the wind." Burckardt never experienced any thing particular at the times when he was exposed to the samoun. Malcolm and Morier, who have traversed the deserts of Persia, and Kerr Porter, who has visited that which is at the east of the Euphrates, agree with him in this point. In the latter country the inhabitants daub their bodies with wet mud, and those of western Africa anoint themselves with fat, in order to prevent the skin from cracking in consequence of too rapid an evaporation.

The deserts of Asia and Africa are the countries where these hot winds shew themselves in all their force. However, in India, which is covered with a rich vegetation, at Chili, in Louisiana, and in the great plains (llanos) of Oronoco, certain winds have a very elevated temperature. All the land-winds, which blow on the coasts of New Holland, are hot and dry. When the N.W. wind prevails for any time at Paramatta, all the plants wither; and the ill success of the attempts at cultivation, undertaken by the English in this country, is due to no other cause. Even in Europe we have the solano of Spain, and the sirocco of Italy, which throw the majority of individuals into a condition of peculiar languor. These winds probably arise in the plains of Andalusia, or on the arid rocks of Sicily; they are much more violent on the north than on the south coast of the island," and it is useless to seek after their origin as far off as the deserts of Africa.