3. Mistral or Circius, and Autun.

THE wind known in Provence, under the name of Mistral or Circus, comes from the Alps to the N.W. It is supposed to contribute greatly to the salubrity of the air, by dispelling the vapours from the marshes and stagnant waters in the southern parts of Provence and Languedoc, where also, as Mr. de Saussure observes, it subjects the inhabitants to great inconvenience, and some. times to considerable losses.

This excellent philosopher imputes it to three causes:

First, The situation of the Gulf of Lyons, which is terminated by a sort of tunnel formed by the Alps and the Pyrennees, and whose sides, therefore, are the principal scenes of its ravages. All the winds between the N. and the W. are united in this gulf, which by Aulus Gellius is called Circius. (Lib. II. cap. 22. See also Pliny, (Lib. II. 46.)

The second is, that this gulf, being to the S, is lower and warmer than the parts adjacent, and as the inferior current of air goes always from the cold to the warm point, the Gulf of Lyons must necessarily be the centre of violent winds, both from the E. and the W.

The third cause is nearly included in the two preceding.

In opposition to the Mistral, another singular wind blows from the east or south-east, which is called autun. It is first perceived near Narbonne, and at Castlenaudari is very violent: this wind, which is hot, produces head-achs, with loss of appetite, and seems to swell the whole body. In the eastern part of Languedoc is frequently felt a cold and very strong north wind, which follows the course of the Rhone, in the valley through which it runs, from north to south, and is called bise, or black. Sometimes, in direct opposition to the latter, blows a sea-wind, which is usually accompanied with a drizzling rain; but when dry, has the same morbid effects as the autun in Upper Languedoc; beside, in the heat of summer, from the coast of Leucate to the Rhone, sea-breezes constantly set in, at nine or ten o'clock in the morning, and, to the great refreshment of the air, last till about five in the evening. Lastly, it is also observable, that at the foot of the Pyrennees, near the village of Bland, in a narrow valley, wholly environed with mountains, except towards the north-west, and through

various channels two or three hundred paces wide, blows a very cold west, or north-west wind, which prevails chiefly in the sum. mer, and then only at night. In clear warm weather this wind is much brisker than in a dense cold atmosphere. In summer it cools the whole valley, and in winter prevents hoar frost; and as it blows only in the night the inhabitants of the village of Bland can winnow their corn at no other time.

EDITOR from De Saussure.

SECTION VI.

Occasional Winds: as Hurricanes, Tempests, Tornados, and Whirlwinds.

1. Hurricanes of the West Indies, and their Causes, in a Communication from Capt. Langford to Mr. Bonavert.

IT has been the custom of our English and French inhabitants of the Caribee islands to send about the month of June, to the native Caribees of Dominico and St. Vincent, to know whether there would be any hurricanes that year; and about ten or twelve days before the hurricane came, they would constantly send them word; and it very rarely was erroneous, as I have observed in five hurricanes, in the years 1657, 1658, 1660, 1665, and 1667. Fron one of these Indians, I had the following prognostics:

1. All hurricanes come either on the day of the full, change, or quarters of the moon. 2. If it be to happen on the full moon, observe these signs, during the change: the skies will he turbulent, the sun redder than usual, a great calm, and the hills clear of clouds or fogs over them, which in the high lands are seldom so: likewise in hollows, or concaves of the earth, or wells, there will be a great noise, as of a storm, and at night the stars will look very large with burs about them, and the north west sky very black and foul, the sea smelling stronger than at other times; and sometimes for an hour or two of that day the wind blows very hard westerly out of its usual course. On the full of the moon you have the same signs, with a great bur about the moon, and frequently about the sun. The same signs must be observed on the quarter days of the moon, in July, August, and September; the months. when the hurricanes are most prevalent; the earliest I ever heard

of, was the 25th of July, and the latest the 8th of September; but the usual month is August.

The method of avoiding the danger is to keep the ship sailable, with good store of ballast, the ports well barred and caulked, the top-masts and tops down, the yards laced a-port, keeping the doors and windows of the ship fast, and she will lie as well as in other storms; thus the ship being in readiness, they may stay in the road till the storm begins, which is always first at north, so to the north-west, till it comes round to the south-east, and then its fury is over. So with the north wind they may run away to the south, to get themselves sea-room, for the drift of the south-west wind, where it blows very fiercely. By these means, I have, by God's blessing, preserved myself in two hurricanes at sea, and in three at shore, greatly to my advantage, as I lost not a sail, yard, or mast in two great hurricanes.

The causes of these hurricanes, according to experimental ob. servations of my time, are these:

1. It is known to men of experience, that to the southward of the tropics there is constantly a trade-wind, or easterly wind, which goes from the north to the south-east all the year round; except where there are reversions of breezes, and inlets near the land; so that when this hurricane, or rather whirlwind, comes in opposi tion to the constant trade-wind, then it pours down with such violence as exceeds any storms of wind. In the hurricane at Nevis, I saw the high mountain that was covered with trees left in most places bare.

2. It is remarked by all men, that have been in those parts where the sun comes to the zenith, that at his approach towards it, there is always fair weather; but at his return southwards, it occasions, off the north parts of the equinoctial, generally much rain and storms, as tornadoes, and the like; which makes the wind in the tornado come on several points. But before it comes, it calms the constant easterly winds; and when they are past, the easterly wind gathers force again, and then the weather clears up fair.

3. The wind being generally between the tropics and the equator easterly, unless at such times as before-mentioned: meeting with the opposition of these hurricanes, which come in a contrary

course to that trade-wind, causes this violent whirl.wind, on the sun's leaving the zenith of Barbadoes, and these adjacent islands; by which the easterly wind loses much of its strength; and then the west wind, which is kept back by the power of the sun, with the greater violence and force pours down on those parts where it gets vent. And it is usual in sailing from Barbadoes, or those islands to the north, for a westerly wind, when we begin to lose our easterly wind, to have it calm, as it is before hurricanes : and then the wind springing up, till it comes to be well settled, causes the weather to be various; but after the settled westerly wind comes fresh, they have been constantly without those shufflings from point to point.

Here it is to be observed, that all hurricanes begin from the north to the westward, and on those points that the easterly wind blows most violently, the hurricane blows most fierce against it; for from the N. N. E. to the E. S. E. the easterly blows freshest; so does the W. N. W. to the S. S. W. in the hurricane blow most violent; and when he comes back to the SE, which is the com. mon course of the trade. wind, then it ceases of its violence, and so breaks up. Thus I take the cause of hurricanes to be the sun's leaving the zenith of those parts towards the south: and secondly, the reverse or rebounding back of the wind, which is occasioned by the calming of the trade-wind.

But it will be objected, why should not this storm be all over those parts of the West Indies, as well as Barbadoes and the Leeward-islands? To which I answer, that it has in about 25 years of my experience, taken its course from the Bermudas to the Caribees; but seldom or never carries such a breadth as from the latitude of 16 to 32 degrees, which are the latitudes of the places; but it has been observed, that when hurricanes have been in Martinico, which is within two degrees of latitude, and two degrees longitude, according to the miles of that circle, yet no hurricane has been in Barbadoes; nor could I ever call any of the former storms at Barbadoes hurricanes, till that last year in 1675. Again it has heen noted, that hurricanes have done the like to the northwards: for when the hurricane has been in Antigua and St. Christopher's, those ships that were only in the latitude of twenty degrees, had no hurricane, but constant westerly winds, reason. ably fair, and then there were no hurricanes in Bermudas; and

when the hurricanes were at Bermudas, the Leeward or Caribee Islands had no hurricane: nor had those islands the hurricane when Barbadoes had it.

It may be also objected, why the hurricane was never known to go farther to the westward than Porto Rico, which lies in or near the latitude of those islands of St. Christopher? To this I answer, that from Porto Rico, downwards, both that island and Hispaniola, as well as other adjacent islands, are of vast magnitude, and very high lands, that of themselves most commonly give reversal or westerly winds at night, through the year; for there, for the reasons aforesaid, the easterly wind, towards night, calms, and those lands afford a land-wind, which the other islands cannot do, by reason of the smallness of those Caribee Islands; but very near the shore, the trade-wind having its full power till this general whirlwind comes, for the reasons aforesaid. I do imagine likewise, to the southwards of Barbadoes, where the tornadoes come fre. quently, there are no hurricanes; nor was there at Barbadoes, when these tornadoes commonly came there, which made some small reversal, though it was but for two or three hours: yet the easterly wind, giving some way by the sun's declining from that zenith, prevents this furious reverse, where it has no vent till it is forced by the violence of the two winds.

[Phil. Trans. 1698.

2. Hurricanes of the Indian Coast.

Dr. Halley seems to consider the hurricanes which blow occasionally in the month of October in the Gulf of Bengal, as of a similar nature to those in the West Indies, in which probably he is right; but at the same time it is evident, that he has been mis. informed, respecting the time they generally happen in the East. He observes that our seamen suppose them to be the breaking up of the monsoon. In this circumstance the mariners have misled

the philosopher; for the hurricanes seldom happen near the change or breaking up of the monsoons, but generally many days. after their commencement, and sometimes about the middle of them. Both the N.E. and S. W. monsoons blow at first in fresh gales, but neither of them encrease to violent hurricanes. It is from very obvious causes already sufficiently explained, that the one dies gradually away before the other begins. But we will first