An Historical Account of the Trade Winds, and Monsoons, Observable in the Seas between and Near the Tropicks, with an Attempt to Assign the Phisical Cause of the Said Winds, By E. Halley

An Historical Account of the Trade Winds, and Monsoons, observable in the Seas between and near the Tropicks, with an attempt to assign the Physical cause of the said Winds, by E. Halley. AN exact Relation of the constant and Periodical Winds, observable in several Tracts of the Ocean, is a part of Natural History not less desirable and useful, than it is difficult to obtain, and it's Phenomena hard to explicate: I am not Ignorant that several Writers have undertaken this subject, and although Varenius (Lib. I. Chap. XXI. Geo. Gen.) seems to have endeavoured after the best information from Voyagers, yet cannot his accounts be admitted for accurate, by those that shall attentively consider and compare them together; and some of them are most evident mistakes; which, as near as I can, I shall attempt to rectify, having had the opportunity of conversing with Navigators acquainted with all parts of India, and having lived a considerable time between the Tropicks, and there made my own remarks. The substance of what I have collected is briefly as follows. The Universal Ocean may most properly be divided into three parts viz. 1. The Atlantick and Ethiopick Sea: 2. The Indian Ocean: 3. The Great South Sea or the Pacific Ocean; and tho' these Seas do all communicate by the South, yet as to our present purpose of the Trade Winds, they are sufficiently separated by the interposition of great tracts of Land; the first lying between Africa and America, the second between Africa and the Indian Islands and Hollandia Nova; and the last, between the Philippine Isles, China, Japan and Hollandia Nova on the West, and the Coast of America on the East. Now following this natural division of the Seas, so will we divide our History into three parts, in the same order. I. In the Atlantick and Ethiopick Seas, between the Tropicks, there is a general Easterly Wind, all the Year long, without any considerable variation, excepting that it is subject to be deflected therefrom, some few points of the Compass towards the North or South, according to the position of the place. The Observations which have been made of these deflections, are the following. 1. That near the coast of Africa, as soon as you have passed the Canary Isles you are sure to meet a fresh Gale of N.E. Wind about the Latitude of 28 degrees North, which seldom comes to the Eastwards of the E.N.E. or passes the N.N.E. This Wind accompanies those bound to the Southward, to the Latitude of 10 North, and about 100 Leagues from the Guinea Coast, where till the 4th degree of North Latitude, they fall into calmes and Tornadoes, of which more hereafter. 2. That those bound to the Caribbe Isles, find, as they approach the American side, that the aforesaid North-East Wind, becomes still more and more Easterly, so as sometimes to be East, sometimes East by South, but yet most commonly to the Northward of the East a point or two; seldom more. 'tis likewise observed, that the strength of these Winds does gradually decrease, as you saile to the Westwards. 3. That the limits of the Trade and Variable Winds, in this Ocean, are farther extended on the American side than the African: for whereas you meet not with this certain Wind till after you have passed the Latitude of 8 degrees on this side; on the American side it commonly holds to 30, 31 or 32 degrees of Latitude; and this is verified likewise to the Southwards of the Equinoctial, for near the Cape of Good-Hope the limits of the Trade Winds, are 3 or 4 degrees nearer the Line, than on the coast of Brazile. 4. That from the Latitude of 4 degrees North, to the afore-said limits on the South side of the Equator, the Winds are generally and perpetually between the South and East, and most commonly between the South-East and East, observing al- always this Rule, that on the African side they are more Southerly, on the Brazilian more Easterly, so as to become almost due East, the little deflection they have being still to the Southwards. In this part of the Ocean it has been my fortune to pass a full year, in an employment that obliged me to regard more than ordinary the Weather, and I found the Winds constantly about the South-East, the most usual point S E b E; when it was Easterly it generally blew hard, and was gloomy, dark, and sometimes rainy weather; if it came to the Southwards it was generally Serene, and a small gale next to a Calme, but this not very common. But I never saw it to the Westwards of the South, or Northwards of the East. 5. That the season of the Year has some small effect on these Trade Winds, for that when the Sun is considerable to the Northwards of the Equator, the South-East Winds, especially in the straight of this Ocean (if I may so call it) between Brasile and the Coast of Guinea, do vary a point or two to the Southwards, and the North-East become more Easterly; and on the contrary when the Sun is towards the Tropick of vs, the South-Easterly Winds become more Easterly, and the North-easterly Winds on this side the Line were more to the Northwards. 6. That as there is no general Rule that admits not of some exception, so there is in this Ocean a tract of Sea wherein the Southerly and S. West Winds are perpetual, viz. all along the Coast of Guinea, for above 500 Leagues together, from Sierra Leona to the Isle of St. Thomas; for the South-East Trade-Wind having passed the Line, and approaching the Coast of Guinea within 80 or 100 Leagues inclines towards the shore, and becomes S. S. E, and by degrees, as you come nearer, it veers about to South, S. S. West, and in with the land South-West, and sometimes West South-West; which variation is better expressed in the Map hereunto annexed, than it can well be in words. These are the Winds, which are observed on this coast when it blows true true; but there are frequent Calms, Violent sudden Gusts called Tornado's, from all points of the compass, and sometimes unwholesome foggy Easterly Winds called Hermitas by the Natives, which too often infest the Navigation of these parts. 7. That to the Northwards of the Line, between 4 and 10 degrees of Latitude, and between the Meridians of Cape Verde, and of the Easternmost Islands that bear that name, there is a tract of Sea wherein it were improper to say there is any Trade Wind, or yet a Variable; for it seems condemned to perpetual Calms attended with terrible Thunder and Lightning, and Rains so frequent, that our Navigators from thence call this part of the Sea the Rainy: the little Winds that are, be only some sudden uncertain Gusts, of very little continuance and less extent; so that sometimes each hour you shall have a different Gale, which dies away into a Calm before another succeeds; and in a fleet of Ships in sight of one another, each shall have the Wind from a several point of the Compass; with these weak Breezes Ships are obliged to make the best of their way to the Southward through the aforesaid six degrees, wherein 'tis reported some have been detained whole months for want of Wind. From the three last observables is thrown the reason of two notable occurrences in the East-India and Guinea Navigations. The one is, why notwithstanding the narrowest part of the Sea between Guinea and Brazil be about 50 leagues over, yet Ships bound to the Southward sometimes, especially in the months of July and August, find a great difficulty to pass it. This happens because of the South-east Winds, at that time of the year commonly extending some degrees beyond the ordinary limit of 40° 36' North Lat. and withall they come so much Southward as to be sometimes South, sometimes a point or two to the West; there remains then only to plie to Wind-ward, and if on the one side they stand away W. S. W. they gain the Wind still more and more Easterly, but there is danger of not weathering the Brazilian shore, or at least the shoals upon that Coast. But But if upon the other tack they go away E. S. E., they fall into the neighborhood of the Coast of Guinea, from which there is no departing without running Easterly, as far as the Isle of St. Thomas, which is the constant practice of all the Guiney Shipps, and which may seem very strange without the consideration of the sixth remark, which shews the reason of it. For being in with the Coast, the Wind blows generally at S.W. and W.S.W., with which Winds they cannot go to the Northward for the Land, and on the other tack they can lie no nearer the Wind than S. S. E., or South; with these courses, they run off the shore, but in so doing they always find the Winds more and more contrary, so that when near the shore they could lie South, at a greater distance they can make their way no better than S. E. and afterwards E. S. E., with which courses they fetch commonly the Isle of St. Thomas and Cape Lopez, where finding the Winds to the Eastward of the South, they keep them favourable by running away to the Westward in the South Lat. of 3 or 4 degrees, where the S. E. Winds are perpetual. For the sake of these general Winds, all those that use the West-Indian Trade, even those bound to Virginia, count it their best course to get as soon as they can, to the Southwards, that so they may be certain of a fair and fresh gale to run before it to the Westwards; and for the same reason those homewards bound from America, endeavour to gain the Latitude of 30 degrees, as soon as possible, where they first find the Winds begin to be Variable; though the most ordinary Winds in the Northern part of the Atlantick Ocean come from between the South and West. As to those furious storms called Hurricanes, which are as it were peculiar to the Caribbe Isles; and which so dreadfully afflict them in the month of August, or not much before or after, they do not so properly belong to this place, both by reason of their small continuance and extent, as likewise because they are not Anniversary, some years having more than one, and sometimes for several years together ther there being none at all. But their Violence is so un concei- vable, and their other Phenomena so surprising, that they merit well to be considered apart. What is here said, is to be understood of the Sea Winds at some distance from the Land; for upon and near the shores, the Land and Sea Brizes are almost every where sensi- ble; and the great Variety which happens in their Periods, Force and Direction, from the situation of the Mountains, Vallies and Woods, and from the various texture of the Soil, more or less capable of retaining and reflecting Heat, and of exhaling or condensing Vapours is such, that it were an endless task, to endeavour to account for them. II. In the Indian Ocean, the Winds are partly General, as in the Ethiopick Ocean, partly Periodical, that is half the Year they blow one way, and the other half near upon the opposite points; and these points and times of shifting are different in different parts of this Ocean; the limits of each tract of Sea, subject to the same change or Monsoon, are cer- tainly very hard to determine, but the diligence I have used to be rightly informed, and the care I have taken therein, has in a great measure surmounted that difficulty, and I am perswaded that the following particulars may be relied upon. 1. That between the Latitudes of ten Degrees and thirty Degrees South, between Madagascar and Hollandia Nova, the General Trade Wind about the S. E. by E. is found to blow all the Year long, to all intents and purposes after the same manner as in the same Latitudes in the Ethiopick Ocean, as it is described in the 4th. Remark aforegoing. 2. That the aforesaid S. E. Winds extend to within two Degrees of the Equator, during the Months of June, July, August, &c. to November, at which time between the South Latitudes of 3 and 10 Degrees, being near the Meridian of the North end of Madagascar, and between 2 and 12 South Latitude, being near Sumatra and Java, the contrary Winds from the N. W. or between the North and West, set in and blow for half the Year, viz. from the beginning of December till May: and this Monsoon is observed as far as the Molucca Isles, of which more anon. 3. That to the Northward of 3 Degrees South Latitude, over the whole Arabian or Indian-Sea and Gulph of Bengall, from Sumatra to the Coast of Africa, there is another Monsoon, blowing from October to April upon the North East Points; but in the other half Year, from April to October, upon the opposite Points of S.W. and W.S.W. and that with rather more force than the other, accompanied with dark, rainy weather, whereas the N.E. blows clear; 'tis likewise to be noted, that the Winds are not so constant, either in strength or point, in the Gulph of Bengall, as they are in the Indian-Sea, where a certain steady Gale scarce ever fails. 'Tis also remarkable, that the S.W. Winds in these Seas are generally more Southerly on the African side, more Westerly on the Indian. 4. That as an Appendix to the last described Monsoon, there is a Tract of Sea to the Southwards of the Equator, subject to the same changes of the Winds, viz. near the African-Coast, between it and the Island Madagascar or St. Lawrence, and from thence Northwards as far as the Line: wherein from April to October there is found a constant fresh S.S.W. Wind, which as you go more Northerly, becomes still more and more Westerly, so as to fall in with the W.S.W. Winds, mentioned before, in those Months of the Year to be certain to the Northward of the Equator: What Winds blow in these Seas, for the other half Year, from October to April, I have not yet been able to obtain to my full satisfaction, for that our Navigators always return from India without Madagascar, and so are little acquainted in this matter; the Account has been given me is only this, that the Winds are much Easterly hereabouts, and as often to the North of the true East as to the Southwards thereof. 5. That 5. That to the Eastward of Sumatra and Malacca, to the Northwards of the Line, and along the Coast of Cambodia and China, the Monsoons blow North and South, that is to say, the N. E. Winds are much Northerly, and the S. W. much Southerly: This Constitution reaches to the Eastwards of the Philippine-Isles, and as far Northerly as Japin. The Northern Monsoon setting in, in these Seas, in October or November, and the Southern in May, blowing all the Summer Months: Here it is to be noted, That the Points of the Compass, from whence the Wind comes in these Parts of the World, are not so fixt as in those lately described; for the Southerly will frequently pass a Point or two to the Eastwards of the South, and the Northerly as much to the Westwards of the North, which seems occasioned by the great quantity of Land which is interposed in these Seas. 6. That in the same Meridians, but to the Southwards of the Equator, being that Tract lying between Sumatra and Java to the West, and New Guinea to the East, the same Northerly and Southerly Monsoons are observed, but with this difference, that the inclination of the Northerly is towards the N. W. and of the Southerly towards the S. E. but the plage venti are not more constant here than in the former, viz. variable 5 or 6 Points; Besides the times of the Change of these Winds, are not the same as in the Chinese Seas, but about a Month or six Weeks later. 7. That these contrary Winds do not shift all at once, but in some places the time of the change is attended with Calms, in others with variable Winds; and it is particularly remarkable, that the End of the Westerly Monsoon on the Coast of Coromandel, and the two last Months of the Southerly Monsoon in the Seas of China, are very subject to be tempestuous: The violence of these storms is such, that they seem to be of the nature of the West-India Hurricanes, and render the Navigation of these parts parts very unsafe about that time of the Year. These Tempests are by our Seamen usually termed, *The breaking up of the Monsoons*. By reason of the shifting of these Winds, all those that sail in these Seas, are obliged to observe the seasons proper for their Voyages, and so doing they fail not of a fair wind and speedy passage; but if so be they chance to out-stay their time, till the contrary Monsoon set in, as it frequently happens, they are forced to give over the hopes of accomplishing their intended Voyages, and either return to the port from whence they came, or else put in to some other Harbour, there to spend the time till the Winds shall come favourable. III. The third Ocean called *Mare Pacificum*, whose extent is equal to that of the other two, (it being from the West Coast of America to the Philippine Islands, not less than 150 degrees of Longitude) is that which is least known to our own or the neighbour Nations; that Navigation that there is on it, is by the Spaniards who go yearly from the Coast of new Spain to the Manilhas, but that but by one beaten track; so that I cannot be so particular here as in the other two. What the Spanish Authors say of the Winds they find in their Courses, and what is confirmed by the old Accounts of Drake and Canalis, and since by Schooten, who sailed the whole breadth of this Sea in the Southern Latitude of 13 or 16 degrees, is, that there is a great conformity between the Winds of this Sea, and those of the Atlantick and Ethiopick; that is to say, that to the Northwards of the Equator, the predominant Wind is between the East and North-East, and to the Southwards thereof there is a constant steady gale between the East and South-East, and that on both sides the Line with so much constancy, that they scarce ever need to attend the Sails, and strength, that it is rare to fail of crossing this vast Ocean in ten weeks time, which is about 13 miles per diem; besides 'tis laid that Stormes and Tempests are never known in these parts: So that here is the ve- y best of Sailing; no want of a fresh fair Wind, and yet no danger of having too much: Wherefore some have thought it might be as short a Voyage to Japan and China, to go by the Streights of Magellan, is by the Cape of Good-hope. The limits of these General Winds are also much the same as in the Atlantick Sea, viz. about the 30th degree of Latitude on both sides; for the Spaniards homewards bound from the Manilhas, alwaies take the advantage of the Southerly Monsoon, blowing there in the Summer months, and run up to the Northwards of that Latitude, as high as Japan, before they meet with variable Winds, to shape their course to the Eastwards. And Schooten and others that have gon about by the Magellan Streights, have found the limits of of S. E. Winds, much about the same Latitude to the Southwards; besides a farther Analogy between the Winds of this Ocean, and the Ethiopick, appears in that, upon the Coast of Peru, they are alwaies much Southerly, like as they are found near the Shores of Angola. Thus far matter of Fact, wherein if the information I have received be not in all parts Accurate, it has not been for want of inquiry from those I conceived best able to instruct me; and I shall take it for a very great kindness if any Master of a Ship, or other person, well informed of the Nature of the Winds, in any of the aforementioned parts of the World, shall please to communicate their Observations thereupon; that so what I have here collected may be either confirmed or amended, or by the addition of some material Circumstances enlarged. It is not the work of one, nor of few, but of a multitude of Observers, to bring together the experience requisite to compose a perfect and compleat History of these Winds; however I am not much doubtful that I have erred in, or omitted any of the principal Observables, whatever lesser particulars may have escaped my knowledge. To help the conception of the reader in a matter of so much difficulty, I believed it necessary to adjoyn a Scheme, shew- shewing at one view all the various Tracts and Courses of these Winds; whereby 'tis possible the thing may be better understood, than by any verbal description whatsoever. The limits of these several Tracts, are designed everywhere by pricked lines, as well in the Atlantick and Ethiopick, where they are the boundaries of the Trade and Variable Winds, as in the Indian Ocean, where they also shew the extent of the several Monfons. I could think of no better way to design the course of the Winds on the Mapp, than by drawing rows of stroaks in the same line that a Ship would move going alwaies before it; the sharp end of each little stroak pointing out that part of the Horizon, from whence the Wind continually comes; and where there are Monsoons the rows of the stroaks run alternately backwards and forwards, by which means they are thicker there than elsewhere. As to the great South Sea, considering its vast extent, and the little Variety there is in its Winds, and the great Analogy between them, and those of the Atlantick and Ethiopic Oceans, besides that the greatest part thereof is wholly unknown to us; I thought it unnecessary to lengthen the Mapp therewith. In the foregoing History are contained several Problems, that Merit well the consideration of our acuteft Naturalists, both by reason of the constancy of the effect, and of the immense extent thereof; near half the surface of the Globe being concerned. The chief of these Problems are. 1. Why these Winds are perpetually from the East in the Atlantick and Ethiopick, as likewise in the Pacifick Ocean, between the Latitudes of 30 North and South. 2. Why the the said Winds extend no farther with Constancy than to the Latitudes of 30dg. 3. Why there should be a constant Southwesterly Wind upon and near the Coast of Guinea. 4. Why in the North part of the Indian Ocean the Winds, which for one half year do agree with those of the other two Oceans, should change in the other half Year, and blow from the opposite Points; whilst the Southern part of that Ocean followes the General Rule; and has perpetual Winds about S.E. 5. Why in these General Trade-Winds it should be alwayes true, that to the Northward of the Equator it is enclined to the Northwards of the East; and in South Latitudes, to the Southward thereof. 6. Why in the Seas of China there should be so great an Inclination from the East to the North, more than elsewhere; with many more, which it would be much easier to propose than Answer. But least I should seem to propose to others, difficulties which I have not thought worth my own time and Paines, take here the result of an earnest endeavour after the true reason of the aforesaid Phenomena, wherein if I am not able to account for all particulars, yet 'tis hoped the thoughts I have spent thereon, will not be judged wholly lost, by the curious in Natural Inquiries. Wind is most properly defined to be the Stream or Current of the Air, and where such Current is perpetual and fixt in its course, 'tis necessary that it proceed from a permanent, unintermitting Cause. Wherefore some have been enclined to propose the diurnal Rotation of the Earth upon its Axis, by which, as the Globe turns Eastwards, the loose and fluid particles of the Air, being so exceeding light as they be, are left behind, so that in respect of the Earth's surface they move Westwards, and become a Constant Easterly Wind. This opinion seems confirmed, for that these Winds are found only near the Equinoctial, in those Parallels of Latitude where the diurnal Motion is swiftest; and I should readily assent to it, if the constant Calms in the Atlantic Sea, near the Equator; the Westerly Winds near the Coast of Guiney; and the Periodical Westerly Monsoons under the Equator in the Indian Seas, did not declare the insufficiency of that Hypothesis. Besides the Air being kept to the Earth by the principle of Gravity, would acquire the same degree of Velocity that the Earth's surface moves with, as well in respect of the diurnal Rotation, as of the Annual about the Sun, which is about thirty times swifter. It remains therefore to substitute some other cause, capable of producing a like constant effect, not liable to the same Objections, but agreeable to the known properties of the Elements of Air and Water, and the laws of the Motion of fluid Bodies. Such an one is, I conceive, the Action of the Suns Beams upon the Air and Water, as he passes every day over the Oceans, considered together with the Nature of the Soil, and Situation of the adjoining Continents: I say therefore, first that according to the Laws of Staticks, the Air which is less rarified or expanded by heat, and consequently more ponderous, must have a Motion towards those parts thereof, which are more rarified, and less ponderous, to bring it to an Equilibrium; and secondly, that the presence of the Sun continually shifting to the Westwards, that part towards which the Air tends, by reason of the Rarification made by his greatest Meridian Heat, is with him carried Westward, and consequently the tendency of the whole Body of the lower Air is that way. Thus a general Easterly Wind is formed, which being impressed upon all the Air of a vast Ocean, the parts impel one the other, and so keep moving till the next return of the Sun, whereby so much of the Motion as was lost, is again restored, and thus the Easterly wind is made perpetual. From the same Principle it follows, that this Easterly Wind should on the North Side of the Equator, be to the Northwards of the East, and in South Latitudes to the Southwards thereof; for near the Line, the Air is much more rarified, than at a greater distance from it; because of the Sun twice in a year Vertical, and at no time distant above 23dg. and a half, at which distance the heat, being as the Sine of the Angle of Incidence, is but little short of that of the perpendicular Ray. Whereas under the Tropicks, though the Sun stay long Vertical, yet he is as long 47dg.off; which is a kind of Winter, wherein the Air so cools, as that the Summer Heat cannot warm it to the same Degree with that under the Equator. Wherefore the Air to the North- wards and Southwards, being less rarified than that in the middle, it follows, that from both sides it ought to tend towards the Equator: This Motion compounded with the former Easterly Wind answers all the Phanomena of the general Trade Winds, which if the whole surface of the Globe were Sea, would undoubtedly blow all round the World, as they are found to do in the Atlantick and Ethiopick Oceans. But seeing that so great Continents do interpose and break the continuity of the Oceans, regard must be had to the Nature of the Soil, and the position of the high Mountains, which I suppose the two principal Causes of the several Variations of the Winds, from the former general Rule: for if a Country lying near the Sun, prove to be flat, sandy, low Land, such as the Desarts of Lybia are usually reported to be, the heat occasioned by the reflection of the Suns Beams, and the retention there of in the Sand, is incredible to those that have not felt it; whereby the Air being exceedingly rarified, it is necessary that this cooler and more dense Air should run thitherwards to restore the Aequilibrium: This I take to be the cause, why near the Coast of Guinea the Wind always sets in upon the Land, blowing Westerly instead of Easterly, there being sufficient reason to believe, that the Inland Parts of Africa are prodigiously hot, since the Northern borders thereof were so intemperate, as to give the Ancients cause to conclude, that all beyond the Tropick was made inhabitable by excess of heat: From the same cause it happens, that there are so constant Calms in that part of the Ocean, called the Raines. (described in the 7th Remark on the Atlantick Sea) for this Tract being placed in the middle, between the Westerly Winds blowing on the Coast Guinea, and the Easterly Trade-Winds, blowing to the Westwards thereof, the tendency of the Air here, is indifferent to either, and so stands in Aequilibrio between both; and the weight of the incumbent Atmosphere being diminished by the continual contrary Winds blowing from hence, is the reason that that the Air here holds not the copious Vapour it receives, but lets it fall in so frequent Rains. But as the cool and dense Air, by reason of its greater Gravity, presses upon the hot and rarified, 'tis demonstrative that this latter must ascend in a continued stream as fast as it Rarifies, and that being ascended, it must disperse itself to preserve the Equilibrium; that is, by a contrary Current, the upper Air must move from those parts where the greatest Heat is: So by a kind of Circulation, the North-East Trade Wind below, will be attended with a South Westerly above, and the South Easterly with a North West Wind above; that this is more than a bare conjecture, the almost instantaneous change of the Wind to the opposite Point, which is frequently found in passing the limits of the Trade Winds, seems to assure us; but that which above all confirms this Hypothesis is the Phenomenon of the Monsoons, by this means most easily solved, and without it hardly explicable. Supposing therefore such a Circulation as above, tis to be considered that to the Northward of the Indian Ocean there is everywhere Land within the usual limit of the Latitude of 30° viz. Arabia, Persia, India &c. which for the same reason as the Mediterranean Parts of Africa, are subject to un-sufferable heats when the Sun is to the North, passing nearly Vertical; but yet are temperate enough when the Sun is removed towards the other Tropick; because of a ridg of Mountains at some distance within the Land, said to be frequently in Winter covered with Snow, over which the Air, as it passes, must needs be much chilled. Hence it comes to pass, that the Air coming according to the general Rule, out of the N. E. in the Indian Seas, is sometimes hotter, sometimes colder, than that which by this Circulation is returned out of the S. W. and by consequence, sometimes the under Current or Wind is from the N. E. sometimes from the S. W. That this has no other cause, is clear from the times wherein these Winds set in: viz. in April, when the Sun begins to warm those Countries to the North, the S.W. Monsoon begins, and blows during the Heats till October; when the Sun being retired, and all things growing cooler Northward, and the Heat increasing to the South, the North-East Winds enter and blow all the winter till April again. And it is undoubtedly from the same Principle that to the Southwards of the Equator, in part of the Indian Ocean, the North-West Winds succeed the South-East, when the Sun draws near the Tropick of Capricorn; but I must confess, that in this latter occurs a difficulty, not well to be accounted for, which is, why this Change of the Monsoons should be any more in this Ocean, than in the same Latitudes in the Ethiopick, where there is nothing more certain than a S.E. Wind all the Year. 'Tis likewise very hard to conceive why the limits of the Trade Wind should be fixt, about the thirtieth degree of Latitude all round the Globe; and that they should so seldom transgress or fall short of those bounds; as also that in the Indian Sea, only the Northern Part should be subject to the changeable Monsoons, and in the Southern there be a constant S.E. These are particulars that merit to be considered more at Large, and furnish a sufficient Subject for a just Volume; which will be a very commendable Task for such, who being used to Philosophick Contemplation, shall have leisure to apply their serious thoughts about it.