without them; the obferving of thofe times is very material, when Sailors go to the fame Point, And hence it appears, that the Part of the Air rarified by Heat, being constantly compreffed on all Sides by the colder and denfer Air, that furrounds it, must be continually driven upwards, as it were like a Vapour, and be there every way equally difperfed to maintain the Equilibrium; fo that the upper Course or Motion of the Air fhall be contrary the under. And thus, as it were by a circular Motion, the conftant Winds that blow near the Earth, produce another Wind that blows a contrary way in the upper Regions of the Air. And this Conjecture is alfo in part confirmed by Experience. For when Sailors are got beyond the Limits of the Trade-Winds, they immediatly find a Wind blowing from the oppofite Quarter. And hence alfo we may eafily explain the Phænomena of periodical Winds, or the return of the Monfoons; which as it scarce admits of any other Solution, fo it confiderably confirms our Hypothefis of the circular Motion of the Air. For fuppofing this circularMotion of the Winds, we must observe that the northern part of the Indian Ocean is every where interfperfed with Land, running out within the Limits of the periodical Winds, viz. Arabia, Perfia, India, &c. which Countries at the time the Sun is in the northern Signs of the Eclip tis, fuffers the fame Heat we or But above mentioned of the inner Parts of Africa; but when the Sun declines to the South they enjoy a temperate Air. this is owing to the long Ridges of Mountains whofe Tops being generally covered with Snow in the Winter; this greatly cools the Air. For this Reafon the general North-Eaft Wind blowing in the Indian Sea is at one time of the Year hotter, and at another colder than the Wind carried circularly from the South-Weft; which is the hottest of these contrary Winds; when it blows thro' the upper Region of the Air; it follows that the under Course of the Air one while moves from the North-Eaft, another from the South-Weft; from the later in the Summer, and from the former in Winter; as we observed in explaining the Phænomena of the Trade- Winds. From the fame Cause it seems to proceed, that the NorthWeft Wind fucceeds the SouthEaft in a certain Tract of the Indian Ocean, lying without the Equinoctial, at the time that the Sun approaches the Tropic of Capricorn. But here we must not conceal, that there is a great dif ficulty in explaining the Reason why in the fame Latitude of the Indian Ocean these Winds are found, there is a perpetual Eaft Wind in the Atlantic without any Variation at all. SECT. VI. or one collateral to the Point they blow to; nor can they return 'till thofe Winds blow the contrary way, which in a certain time they will do and continue to blow fo long the other way. Tho' they do not immediately begin to blow the other way, when they have done blowing the former way; but after fome Days more, or lefs, in which the Winds are unfettled; and the Sailors fometimes furprized with Calms; and the Sea-Waves move feveral Ways; yea and frequent Storms arife. Some of the Monfoons return twice in a Year, but not with the fame Vehemence. 1. IN that part of the Atlantic Ocean which lies in the Torrid Zone, and that alfo in the Temperate, the North Wind blows frequently in the Month of October, November, and January; and thefe Months are the best times to go from Europe to India, that they may get beyond the Equator with the help of them; for it hath been found, that fome Ships that had gone from Europe in March have not come fooner to Brafil than thofe that left it in October; coming both to it in the Month of February; being helped by the North Winds. But because this Wind is not fo conftant and certain, Seamen do not reckon it among the Monfoons. Nor is it easy to give the caufe of that Wind in thefe Months; except we refer them to the great quantity of thick Vapours at that time, or the conftant preffure then made by the heavy Clouds. And they that wintered in Nova Zembla fay, there was a conftant North Wind all the Winter; which could not be by a Rarefaction of the Air made by the Sun, which was under the Horizon. Yet we It is alfo very difficult to explain why the Limits of the contant Winds fearce reach beyond thirty Degrees of Latitude; as allo why Monfoons are found only in the northern part of the Indian Ocean; whilft in the South part the North - East Wind perpetually reigns. think it may be maintained in the general, that most of these Monfoons come from the melting of the Snow, or the diffolution of the Clouds in the North and South Places, efpecially the Mountains which I am apt to believe, because these Monfoons blow, for the most part, from the North or South, or the Points collateral; and becaufe the Snow and Clouds in the northern Parts are diffolved by the Sun; efpecially in that half Year it goes thro' the North part of the Ecliptic, the Monfoons are then from the North, and in the other half from the South. THE Cause of these Monfoons in the Sea, blowing mostly from collateral Points, as South-East, North-East, or those next them, feems to be from the different Situation of the Places in which the Snow and thick Clouds are; or from the general Wind which may divert them to another Point: for that Wind blowing to the West, and the Monfoons tending North and South, they muft hinder one another; and thus go in a Point between the Cardinals. But the South-Weft and North-Weft Monfoons are rare and weak, and are scarce to be reckoned Monfoons, when the North and South Winds feem fometimes by accident to decline to the Weft, but are drawn to the Eaft by the general Winds. There are required for giving the Caufes of the great variety of the Monfoons in different Places, more accurate Obfervations, not of one Year only, but of feveral Years; with the Times of the Winter, Rains, Snows, and of the Mountains in thofe Places from which the ftated Winds blow. We fhould also know the Motion and Age of the Moon; which may cause a Change in this Matter. 2. IN the Month of July, and fome Months near it, the South Winds blow at Cape Verd in Africa (when there is a Winter of Rain there) which feems SECT. VI. feems to be from the fame Cause that makes the North Winds blow in Winter, in our Zone. 3. A T the Cape of Good-Hope the North-Eaft Wind blows in September. 4. AT Patanen (which is a Kingdom and a Town of the fame Name in India, beyond the Mountains of the Gate) there are conftant Rains, and a North-East Wind that blows; but in the other Months an Eaft Wind blows thro', and 'tis Summer then. 5. ABOUT Sumatra the Change of the Monfoons is in November and December. 6. IN the Ifland of del Mayo, one of the salt Illes in the Azores, there blows a vehement Wind in the end of Auguft from the South, with much Rain, which moiftens the Land, that is naturally dry, and then the Grafs begins to fpring up; which fattens a great many Goats there, against the end of December. 7. IN the Kingdom of Congo in Africa, from the middle of March to September; when the Winter reigns there, the North, Weft, and North-West Winds blow, or others intermediate, which force the Clouds together on the Tops of the Mountains, and caufe a dark Air with Rain (fee the next Propofition): but from September to March the Winds are contrary, being South, East, and South-Eaft, and others intermediate. We have taken thefe differences of the anniversary and stated Winds from the Obfervations of Sailors, who call them Monfoons when they blow for a great way on the Sea. We would now treat of their Causes; but we want to know the Mountains, Snows, and the Times of their diffolving, and other things; nor are the Obfervations of Sailors fo exact as to deferve an accurate Enquiry into their Caufes. THE Monfoons that are moft famous are; 1. Thofe in the Indian Ocean, between Africa and India; and at the Molucca Ifles they begin in January, and blow to the Weft fix Months to the beginning of June; and in September and August it begins to blow to the Eaft; and in June, July, and Auguft, there is a Change of the Monfoons and raging Storms from the North. But when we fpeak of Winds blowing to the Eaft or Weft, we understand alfo the collateral Points. 2. BUT at the Shores, the eastern Monfoon varies much; fo that only from January to the end of March or the middle of May, the Ships that go to Perfia, Arabia, Mecha, and Africa, only fail when they come from India on this Side the Gate, or the Shore of Malabar; for the Storms rage in the end of May, and all June, July, and Auguft, with a North Wind often, or a raging North-Eaft Wind; therefore no Ships go from India on this Side the Gate in thefe Months. But on the Shore of India, beyond the Gate, or the East Shore, or the Shore of Cormandel, they know nothing of thefe Storms. They fail in the Month of September from Ceylon and Java, and other Ifles there to the Molucca Ifles; for then the Weft Monfoons begin, that hinder the general East Wind: but when they come to the fifteenth Degree of South Latitude, from the Equator, the weftern Monfoon is fenfible in the Indian Ocean, and a general South-Eaft Wind fills the Sails. 3. FROM Cochin to Malacca, i. e. from Weft to Eaft, they begin to fail in March; for then the Weft Monfoons begin there, or rather the NorthWeft Wind blows often. 4. IN the Kingdom of Guzarat, i. e. in India on this Side of the Gate, the North-Weft Winds blow the half of the Year from March to September, and the other half Year the South Winds. and that without much hindrance by other Winds. I |