yet more frequently blowing from the South-Weft Points.

II. As in the Atlantic, fo in the Indian Ocean, the Winds are partly conftant, and partly periodical; that is, they blow for fix Months in one Point, and the fix following in the very oppofite Point. Both thefe Points, and the Seafons at which they turn to the oppofite Sides, differ with the Places. And tho' it be matter of great difficulty to obferve how the Tracts of the Sea may be defined when fubject to each periodical Wind,

or

Monfoons as they call them: Yet having ufed clofe Application, I don't fcruple believing the following Particulars.

I. Betwixt ten and thirty Degrees of South Latitude thro' that Tract of Sea bounded by St Laurence's Ifland and New Holland, the South Eaft Wind blows all the Year; yet fo as to be fomewhat nearer the Eaft than South; juft as about the fame Latitude in the Atlantic Sea, we above fhew'd them to be.

2. That South-Eaft Wind blows, from May to November, to the fecond Degree from the Equator; in which Month of November, between the third and tenth Degrees of South Latitude, near that Meridian which paffes thro' the northern Part of St Laurence's Ifland,

as alfo between the second and twelfth Degree about Sumatra and Java, arifes a Wind contrary to the former, viz. the North Weft, which reigns the other fix Months; viz. from November to May. This Motion of Winds is found to extend to the Molucca Islands.

3. Northward from the third Degree of South Latitude, in all the Arabian or Indian Sea, and in the Bay of Bengal, from Sumatra as far as the Shore of Africa, is obferved a Motion differing from the former, breathing from the North-East Climates from October to April, which for the next fix Months riles from the oppofite, or South-Weft, Points. Then it breathes more violently, and brings Clouds and Rain; but upon the blowing of the NorthEaft Wind the Heavens become ferene. But it is to be observed, that in the Bay of Bengal the Winds keep neither their Force nor their Points with the fame Conftancy, as in the Indian Sea. Alfo the SouthWeft Winds, near the African Shore, decline more fouthward; near India, more weftward.

4. On the South of the Equator, that Tract of Sea, which lies between Africa and Laurence Ifland, and which goes as far as the Equator, seems to appertain to the Motion of Winds juft now laid down. For in thefe Places the South-Weft Wind blows from Odober to

April, fomewhat nearer the South; but fuch as fail to the North perceive it decline towards the Weft, which at length coincides with the periodical South-West Wind, which they fay blows at that Seafon of the Year, from the North Side of the Equator. But what Winds during the rest of the Year, reign in that Sea, I cannot fufficiently determine: because our Sailors, in their return from India, fteer their Courfe beyond the Ifland of St Laurence. This only I could learn, that the Wind for the moft part comes from the eastern Points, fometimes declining to the North, and at other times to the South.

5. On the Eaft of Sumatra, and North of the Equator, as alfo on the Coafts of Camboia and China, the periodical NorthEaft Winds come nearer to North, as do the South-Weft Winds to South. And this is obferved to hold 'till you have gone beyond the Philippine Islands on the Eaft, and as far as fapan towards the North. In the Month October, or November, a northerly Gale arifes; and in May a foutherly, which continues from that time during the whole Summer. But it is to be marked, that the Points of the Winds are not fo fteadily fixed in these Parts, as they are in other Seas: fo that fometimes the South Winds decline a Point or two towards

AMONG

the Eaft, as the northern do towards the Weft: which feems to take it's rife from the Bulk of the Lands, that are every where interpofed in this Sea.

6. About the fame Longitude on the South of the Equator, viz. in the intermediate Space between the Islands Sumatra and Java lying to the Weft, and New Guinea to the Eaft, nearly the fame periodical Winds blow from the North or South; but fo that the North Winds incline to the Weft, and the South to the Eaft. And these blow with the fame inconftancy and fhifting of the Point, as thofe of the Quarter abovementioned; but the Motions begin four or fix Weeks later than in that Sea.

7. The Change of thefe Motions does not happen fuddenly, or at once; but in fome Places there are Calms, and in others changeable Winds. And often on the Shore of Cormandel, towards the end of the accidental Motion; and the two laft Months there arise furious Tempefts in the Chinese Sea; with the periodical Wind at South.

All Navigation in neceffarily regulated according to thefe Winds; for if Sailors fhould delay the Seafon 'till the contrary Motion begins, they must either fail back, or go into Harbour, and wait for the return of the Trade-Wind.

III. The third, or Pacific Ocean, ftretches nearly as far as the two former taken together; viz. one hundred and fifty Degrees, from the western Shore of America to the Philippine Ifles. But as this is failed by very few befides the Spaniards, from Spain to the Manilhas, and that only once a Year; whilft they conftantly take the fame Courfe; it remains in a great Meafure unknown to us; and cannot therefore be defcribed with the fame exactness as the reft. Thus much is certain; as well from the Obfervations of the Spaniards, as others, that the Winds which blow here have a great affinity with thofe in the Atlantic; for the NorthEaft blows to the North of the Equator, and the South-Weft to the North of the fame, with fuch a Strength and Conftancy, that the valt extent of this Ocean may be failed in about ten Weeks, without fhifting the Sails. Here alfo are no Tempests, fo that failing is no where fo commodious, as neither Wind is wanted, nor it's Violence to be feared. Whence fome imagine, that it is as fhort a Voyage thro' the Streights of Magellan to China or Japan, as by doubling the Cape of GoodHope.

Thefe Trade-Winds extend not to above thirty Degrees of Latitude on both Sides of the Equator, as in the Atlantic O cean. This appears in part from

Sea;

the Course observed by the Spaniards returning from the Manilhas to New Spain; for by means of the fouthern Wind, which blows in these Islands during the Summer Months, they fail to the South up to the Latitude of Japan; where they firit meet with various Winds that will carry them to the Faft. And in part again, from the Obfervations of Schoo ten and others, who failing to India thro' the Streights of Magellan, found almost the fame Diftance of the Winds on the South of the Equator. And in this alfo the Winds of the Pacific agree with those of the Atlantic Ocean; that near the Coast of Peru they approach to the South, as on the Coaft of Angola.

That the Reader may form the better Notion, we shall add a Figure (fee Fig. 30.) reprefenting to the Eye all the Quarters and Points of all the Winds. The Limits of each Tract are marked with pricked Lines, as well in the Atlantic, whether they separate the variable Winds from the conftant, as in the Indian Ocean, where they alfo separate the different Monfoons from one another. The eafieft way of marking the Quarters of the Winds feemed to be by a Series of little fharp-headed Lines, pointing alternately to the Parts of the Horizon from whence the Winds blow. But as the Pacific

Pacific Ocean is fo extreamly large, and yet in a great meafure unknown to us; I was unwilling to exhibit the whole, to prevent enlarging the Map beyond a reasonable size.

There arifes, from the Premises, various Questions worthy the Confideration of Philofophers: the principal are thefe. 1. Why does the Wind in the Atlantic and Pacific Ocean, continually blow from the Eaft within thirty Degrees on both Sides the Equator? 2. Why is not the like conftant Wind found beyond these Limits? 3. Why is the West Wind found perpetual near the Coast of Guinea? 4. Why, in the northern Part of the Indian Ocean, do the Winds for fix Months confpire with the aforefaid Winds; and for the other fix, blow from the oppofite Point; whilft that part of the fame Ocean which lies on the South Side of the Equator, has no other Winds but what are found in other Seas? 5. Why do the conftant Winds on the North Side of the Equator incline to the North; and on the South Side to the South; 6. Why in the Chinese Sea, chiefly, is there fo remarkable an Inclination of the Winds to the North?

For the folving of these Problems, I offer the following Particulars to the Confideration of the Learned.

Wind is properly defined a Current, or Motion of the Air,

ly

which if conftant, or perpetual, must have a permanent or conftant Caufe. Some imagine this Caufe to be the annual Revolution of the Earth about it's own Axis. This might perhaps be allowed, if almost continual Calms were not found in the Atlantic Ocean near the Equator; and alfo West Winds upon the Coast of Guinea, and western Trade-Winds in the Indian Ocean, under the Equator. Befides, the Air being a ponderous or gravitating Body, it will acquire the fame Velocity as the Earth; and as it rolls along therewith in the annual Motion, it will feem more to do it in the diurnal; which is not above a thirtieth fo fwift as the other. So that fome other Caufe must be fought for.

The true Caufe we judge to be the Sun continually permeating the Ocean; with the Addition of the Nature of the Soil and adjacent Country.

For by the known Laws of of Hydroftatics, that part of the Air which is most rarified by Heat, is the lighteft; and confequently the others tend towards it, 'till an æqilibrium be obtained. But as the Sun continually moves towards the Weft; it is manifeft that the Air, most heated by it's direct Rays, muft thus move the fame way; and therefore the whole Mafs of the lower Air. By this Means there is produced a general Eaft Wind, which Kk 4 putting

putting all the Parts of the Air, refting upon the vaft Ocean into Motion, they all keep their own Motion 'till the Sun returns; whence the Eaft Wind becomes perpetual.

And hence it follows, that the Wind on the North or South Side of the Equator, ought to incline towards the North or South. For as the Air near the Equator receives the Sun's Rays perpendicularly, twice every Year, and never more inclined than thirty Degrees, it must of course be greatly rarified by fo great a Heat. Near the Tropics alfo the Sun is vertical, for a confiderable Time; but as it is diftant therefrom forty-feven Degrees for no less a time; the Air hence becomes fo cold that it cannot afterwards be brought to the fame Degree of Heat, which it receives under the Line. Whence the Air, being lefs rarified on both Sides the Equator, flows to the middle. And this Motion being compounded with the Eaft Wind abovementioned, explains all the Phænomena of the general Winds; which, if the Surface of the Earth was every where covered with Sea, would blow with the fame conftancy they do in the Atlantic and Ethiopic Oceans.

But as the Ocean is interrupted with fuch large Tracts of Land, regard must be had to the Nature of the Soil, and the

without

Pofition of high Mountains; to which two Caufes the Changes of the Wind feem principally affignable. For when a Country lying near the Equator is low and fandy, the Heat of the Sun, reflected by the Sand is fo great as to be almost incredible. And thus the Air of this Place being highly rarified; the denfer Parts of the Air will neceffarily move thither to reftore the Equilibrium. Whence I judge, that near the Coaft of Guinea the Wind conftantly blows to the Land; as it is exceeding probable that the inner Parts of Africa are violently heated: fince even the most northern Parts thereof, by reafon of their Heat, made the Antients believe all the Parts beyond the Tropics uninhabitable.

And hence we may explain those frequent Calms; mentioned above in our fixth Observation. For as that Part of the Atlantic lies betwixt the Weft Winds perceived near Guinea, and the conftant Eaft Wind that blows in the Parts fomewhat more to the Weft, the Air lying thereon giving way to neither of these contrary Winds, keeps it's Place, and makes a Calm. And the Air not able to fupport the Vapours here plentifully raised by the Heat, as being more light and rarified; the oppofite Winds frequently caufe the Rains to fall heavy.

And