bably by way of marking the origin of the term), is of great fervice to fhips in trading voyages. "But the trade wind, as it has hitherto been called, blows always, not at certain times, from the eaft toward the weft; and in all parts of the ocean within the tropics, where it is, beyond the influence of the land, it is fubject to very flight variations from that point. In the northern tropic, a few degrees beyond that fide of the equator, it varies only a point or two, inore or lefs, to the northward; and fo likewife at the fame diftance to the fouth of the equator, it inclines occafionally rather more or lefs to the fouthward. But as thofe winds are equally ufeful both to trading fhips and men of war, they might, I think with more propriety, be called the perennial winds, being the only current of air which conftantly moves the fame way in any part of the world. In the following treatife, accordingly, I fhall beg leave to diftinguish them by the name of the northern and fouthern perennial winds. "The term monfoon is not derived, as is often fuppofed, from the name of a famous mariner, but from the Perfian word Moufum, Seafon. There are two winds of this name, diftinguifhed in India by the N. E. and S.W. monfcons, which in fome refpects may be faid to change alternately every fix months, according to the fituation of the fun in the ecliptic." P. xviii. "The ancients, no doubt, clearly understood the nature of winds, but thofe laft mentioned muft of courfe have been perfectly unknown to them. The difcovery of fuch as prevailed at a difance from land, was referved for the more enlightened ages of the fifteenth and fixteenth centuries, when mariners, by the help of the compals, could venture to extend their v⚫yages beyond fight of land; and indeed when lights of various kinds, connected with this fubject, fuddenly burit forth upon the world, and difpelled the mifs of error, with which mankind had long been furrounded. "Among ft the principal caufes which produced thefe advantages in avour of modern times, may be confidered the revival and confirmation, if not the difcovery, of the true planetary fyftem of Copernicus." P. xx. "Whilft confulting maps, when the picture of them immediately ftrikes the eye, no error or confufion can arife to thofe who are in any degree converfant in geography, from places being defcribed by different appellations; but the perfon who in reading fhould meet with a remark relating to the Red Sea, would in all probability not know the place alluded to, if mentioned by the name of the Arabian Gulf, as it is frequently called by different geographers: neither would he clearly com prehend that that which is fometimes called the Arabian Sea, is at other times named the Indian Sea. Befides, both thefe are equivocal terms; for the former might relate either to the Gulf of Sind, or what is ufually called the Red Sea, as the latter might as well denote any other branch of the Indian Ocean. "In the map, therefore, I have adopted the name of the Arabian Gulf, for the Red Sea; of the Gulf of Sind, for what is often called the Arabian Sea; and I have fubftituted the Gulf of Bengal, for what is ufually termed the Bay of Bengal. The fame definition, perhaps, will nearly apply to all feas, gulfs, and bays, namely, that they are a part of the ocean, or feä, nearly furrounded by land, excepting where they immediately communicate with the ocean; but all of them are eatily diftinguished by their different magnitudes, for there may be many gulfs in one fea, and many bays in ore gulf; as the Gulf of Finland, and the Gulf of Bothnia, in the Baltic Sea; and the Bay of Campeachy, and the Bay of Honduras, in the Gulf of Mexico. The Mediterranean and the Baltic are properly fas. The Cafpian and the Dead Seas, not having any apparent communication with the ocean, may I think, be diftinguished by the priticular name of Inland Seas." P. av. EXTRACTS. CAUSE OF LAND AND SHA BEFFZF9: ON THE FORMATION OF CLOLDS, &c. "MR. Clare, in his Treatife or the Motion of Fluids, fhows the caufe of thefe breezes by an eafy and familiar experiment.. Take,' he fays, a large difh, fill it with cold water, and into the middle of this put a water-plate 'filled with warm water: the firft will • reprefent reprefent the ocean, the latter an inland, rarefying the air above it. Blow out a wax candle, and if the place be ftill, on applying it fucceffively to every fide of the difh, the fuliginous particles of the fmoke, being vifible and very light, will be feen to move towards the difh, and rifing over it, point out the courfe of the air from fea to land. "Again, if the ambient water be warmed, and the difh filled with cold water, when the fmoking wick of the ⚫ candle be held over the centre of the plate, the contrary will happen, and how the courfe of the wind from land to fea. "During the continuance of the land and fea breezes on the coafts of Coromandel and Malabar, both in the N. E. and S.W. monfoons, the wind on fhore seems regularly to follow the courfe of the fun, and palles very perceptibly round every point of the compafs in twenty-four hours. "Thefe winds blow conftantly every year on the coaft of Coromandel to the latter end of January, and continue during February and to the beginning of March, fubject to very flight variations; but as the fun approaches towards the vernal equinox, the winds again become variable for fome days, as they were about the autumnal equinox, until his declination is upwards of 7 degrees N. when the S.W. monfoon fets in, and often on the fouth part of the coaft, with confiderable violence. This change or reflux of air appears to be put in motion by the fame means as that which comes from the oppofite quarter; for as the fun's altitude increates daily in the northern hemisphere, the extenfive body of land in the N. E. part of Asia must become much hotter than the ocean, and confequently a confiderable degree of rarefaction will be produced over that part of the continent, whilft at the fame feafon an immenfe body of cold air will come both from the Indian Ocean and the continent of Africa, in the fouthern hemifphere, to reftore the equilibrium. The principal tracts of land of different temperatures on the two conti nents, bearing very nearly N. E. and S.W. of each other, will therefore become alternately the two opposite extreme points of rarefaction and condentation, and necessarily, according to this theory, be the immediate caufes of the N. E. and S.W. monfoons. "But to thofe who have not confidered the nature of the monfoons in India, it may appear fomewhat inconfiftent with this theory, that the N. E. monfoon, which blows with great force in October and November on the Coromandel coaft, is fcarcely felt a few degrees to the weitward on the Malabar coast, and so vice versa. The S.W. monfoon, which blows with great ftrength on the Malabar coaft in April, May, June, and July, is never felt with any degree of violence on that of Coromandel after its commercement, nor even then, excepting very far to the fouthward. It is true, both coafts are in the northern hemifphere, and might be fuppofed fubject to the fame effects from the fituation of the fun; and fo they certainly are in fome degree, for the wind blows nearly in the fame direction on both fides the peninfula; but on referring to the map, it will be found that the two coafts are feparated by a double range of mountaing, running almoft N. and S.; the one immediately bounding the coaft of Malabar, the other nearly in the middle of the peninfula, called the Ballagat, or country above the Paffes; both which ferve alternately as a fcreen to either coaft during the different monfoons. Befides, they not only break the force of the wind, or current of air; but thefe mountains, being lefs electrified than the clouds coming from the fea, attract them; and it is fuppofed, when nearly in contact, take away their electrical fire, and caufe them to precipitate the water they contain. "It was not, originally, the immediate object of this work to account for the immenfe quantity of rain which conftantly falls every year in India, during the different monfoons; nor fhall I endeavour to folve this difficulty without very great doubt of fuccefs; neverthelefs, as violent rains invariably accompany the change of the monfoons, it feems neceffary to make the attempt, more especially as the two fubjects feem on all occations to be intimately related, or rather infeparably connected, "Clouds are generally believed to be formed by vapours raifed by folar or fubterraneous heat from moisture in the earth, or in greater quantities from 3 E 2 water water itself, and when fo raised they are kept fufpended in the middle regions of the atmosphere in the form of clouds, until by fome means not yet indifputably afcertained, the water is again precipitated to the earth in rain. "It may be neceffary to premife, that in treating of this fubject I fhall generally make ufe of the word vapour for that which arifes from water or any other fluid, and of the term exhalation for that which comes from the land. land. Those vapours, which have 'both common and electrical fire in ' them, are better supported than those, which contain only common fire; for when vapours rife into the coldeft region above the earth, the cold will not diminish the electrical fire, if it doth the common. Hence clouds 'formed by vapours raised from fresh 'waters within land, from growing vegetables, moift earth, &c. more fpeedily and eafily depofit their wa'ter, having but little electrical fire to repel and keep the particles feparate. So that the greateft part of the water 'raised from the land is let fall on the • land again; and winds blowing from the land to the sea are dry, there being little ufe for rain on the fea; and to rob the land therefore of its moifture, in order to rain on the sea, would be contrary to the unerring ⚫ diftributions of Nature. moved by winds, may bring it over the middle of the broadeft continent from the middle of the wideft ocean. How these ocean clouds, fo ftrongly 'fupporting their water, are made to depofit it on the land where it is 'wanted, is next to be confidered. "If the ocean clouds are driven by winds against mountains, thofe 'mountains, being lefs electrified, at "By fome authors it is fuppofed, that both vapours and exhalations are fmall veficulæ detached, as before obferved, from the earth or water by heat, and which must be fpecifically lighter than the air, or they could not afcend. When they have pafied through the denfer mediumn near the earth, attracted by the dry air above them, they continue to afcend until they ar- "But clouds formed by vapours rive at a cold region, where they be- raifed from the fea, having both fires, come condenfed, and remain fufpended, and particularly a great quantity of as before obferved, in the form of 'the electrical, fupport their water clouds. In this ftate they continueftrongly, raife it high, and being floating, till by fome new agent they are converted into rain, hail, fnow, mift, &c. Others again, who equally admit that the clouds are formed by thefe veficulæ, think that they coalefce in the upper regions of the atmosphere, forming into little maffes until they become too heavy to be any longer fufpended, and then defcend in rain. But this hypothefis cannot be well founded, for the vapours are perpetually ascend-tract them, and on contact take away ing into the upper regions of the atmofphere, which are always cold; and confequently, according to this theory, they would again be precipitated in rain as foon as they have arrived at a certain height, which would almost conftantly produce regular fhowers. The fame objection applies to the fyf-the vales in rivulets, which united tem of Dr. Derham, who accounts for rain by fuppofing the veficulæ to be full of air, which (he fays) becoming contracted in the colder regions, the watery fhell, thus thickened, becomes heavier than the air, and is precipitated in rain by its comparative weight. But "When a ridge of mountains thus Dr. Franklin, in his Obfervations on 'dams the clouds, and draws the elec Electricity, feems to account most ra- 'tric fire from the cloud first approachtionally for the formation of the cloudsing it, that which next follows, when and precipitation of rain. The fun fupplies (or feems to supply),' he says, common fire to all vapours raifed ⚫ from the fea, or exhalations from the their electrical fire (and being cold, their common fire alfo); hence the particles clofe towards the mountains, and towards each other. If the air 'was not much loaded, it would only 'fall in dews on the mountain tops and fides, form fprings, and defcend into make larger ftreams and rivers. But being much loaded, the electrical fire is at once taken from the cloud, and on leaving it the particles coalefce for want of that fire, and fall in heavy showers. it comes near the firft cloud (now deprived of its fire), flashes into it, and begins to depofit its own water. The 'first cloud again flathing into the ⚫ mountains, mountains, the third approaching cloud, and all the fucceeding ones, act in the fame manner as far back as ⚫ they extend, which may be over many ⚫ hundred miles of country.' fluid moving from all points horizon'tally towards a centre muft either 'afcend or defcend; but air flowing ' on or near the furface of land or wa" ter, from all fides towards a centre, muft neceffarily at that centre afcend, the land or water hindering its defcent. But if thefe concentring currents be in the upper region of the atmosphere, they may indeed defcend and caufe a whirlwind; and when this current has reached either the "It is evident from the geographical fituation of the peninfula of India, that the clouds which are conveyed over it in both monfoons, must be saturated with moisture. In the N. E. monfoon the vapours will be raised from the fea in the Gulf of Bengal, and as they approach the land on the coaft of Coro-earth or water, it must spread, and mandel, the clouds, in the manner above described, will be made to difcharge their contents in great torrents of rain. So likewife in the S.W.monfoon, the vapours will be raised in the Gulf of Sind and the Indian Ocean, and they alfo in the fame manner will difcharge their contents on the Malabar coaft and amongst the Ballagat mountains. "But as an additional proof of the truth of this hypothefis, it may be obferved, that the quantity of rain which falls in the principal part of South America, as well as in this part of India, is constantly in proportion to the height and extent of the mountains, to the length of time that the wind continues to convey the clouds towards the Jand, and to the extent of the fea or ocean whence the water is evaporated which forms thofe clouds, "The principal features of both these countries bear a striking refemblance to each other; thofe of the peninfula of India being in miniature almost precisely the fame as those of America in the fame parallel of latitude. The former is fituated between the Gulf of Bengal and the Gulf of Sind; the latter between the South Atlantic and the Pacific Oceans. Both countries have a lofty ridge of mountains, which run through the centre of them from N. to S.; and both have large rivers, apparently in exact proportion to the fize of their refpective mountains, which discharge themselves towards the E. into the sea." P. 44. WHIRLWINDS-ISLAND OF BERMUDAS. "WHIRLWINDS,' fays Dr. Franklin, in one of his letters on phifofophical fubjects, are of two kinds; one from the air afcending, and the other from the air defcending. A probably blow with great violence to a confiderable distance from the cen'tre. Of the two kinds of whirl'winds, that which ascends is the moft 'common; but when the upper air defcends, it is perhaps in a greater 'body, extending wider, as in thunder 'gufts, and without much whirlwind." If then this opinion be well founded, a common gale of wind, of moderate extent and thort duration, may be fuppofed to proceed from the former; but when violent, of long continuance, and with less variation, from the latter. "It would not, perhaps, be a matter of great difficulty to afcertain the fituation of a fhip in a whirlwind, by obferving the ftrength and changes of the wind: if the changes are fudden and the wind violent, in all probability the fhip must be near the centre or vortex of the whirlwind; whereas if the wind blows a great length of time from the fame point, and the changes are gradual, it may be reasonably fuppofed the fhip is near the extremity of it. "Another extraordinary circumftance respecting these hurricanes thould likewife be mentioned, as tending to a difcovery of their caufes; that they moft frequently, it might perhaps with propriety be faid always, occur near large bodies of land, but are not known at fea within the tropics, at least in that part of the ocean remote from the continent, or even at a confiderable dif tance from extenfive islands. It is a well-known fact, as the name itself implies, that the Pacific Ocean is exempt from tempefts. So likewise is the middle of the South Atlantic Ocean, particularly from the equator to the la titude of 16 degrees S. A violent gale of wind, for inftance, was never known at the little island of St. Helena, which lies at the diftance of nearly a thousand miles from the weft coaft of Africa, and ftill further from the eaftern coaft of America. The mean temperature of St. Helena is, I believe, 72 degrees inftead of 79, which is the mean temperature of places on the continent, in the fame parallels of latitude; but the variations there throughout the year, both of the thermometer and barometer, are very trifling. It must here be again remembered, that the vapours raifed from the ocean have a larger portion of both common and electrical fire, and are, therefore, more firmly fupported in the form of clouds than thole which come from the land; that in thefe oceans an equal temperature almost constantly prevails, and that all the circumambient air is filled with homogeneous vapours. In every wide expanfe of ocean, therefore, unbroken by a continent or extenfive ifland, no fudden changes are likely to take place in the atmosphere; but, on the contrary, where the clouds, which are formed by exhalations from extenfivebodies of land, approach thofe which are derived from the ocean, violent and fudden alterations muft neceffarily occur; for, as it has been frequently before remarked, the land clouds will attract both common and electrical fire from those clouds which come from the ocean, until the equilibrium is reftored; and during this operation fuch changes muft neceffarily happen in the atmosphere, as will produce ftrong currents of air, and in general whirlwinds. Near every part of the continent of Afia, in the Gulf of Bengal, on either coaft of Africa, near the island of Madagascar, and even in the vicinity of the islands of Mauritius and Bourbon, where alfo there are volca noes, whirlwinds occafioned by fudden changes in the atmosphere will, at certain feafons, frequently occur. But in the Pacific Ocean, and in the central parts of the North and South Atlantic, they will feldom happen. Ships in croífing the North Atlantic fcarcely ever meet with hard gales of wind be fore they approach the Western Iflands, where likewife there are volcanoes. But in the islands of Bermudas, which are fituated in the Northern Atlantic Ocean, about the latitude of 32 degrees N. and at the diftance of fix hundred miles from the coaft of America, hurricanes, I believe, are almoft unknown; but thunder and lightning, with temporary gufts of wind, or violent fqualls, are very common. Were thefe iflands of lefs extent, cr had they been placed within the tropic, it is probable they would have been as exempt, even from tempefts, as St. Helena, or the islands in the Pacific Ocean; but fituated in the temperate zone, and not very remote from Ame rica, they are fubject occafionally to fudden and violent gifts from the N.W. which probably onginate on that contiment. The Bermudas, however, en joy "It is to be regretted that invalids in Europe, especially thofe afflicted with pulmonary complaints, do not prefer a voyage to the islands of Bermudas, to vifiting either the fouth of France or Lifbon; for the mild regular climate of these islands is infinitely preferable to that of any place on the continent, and even to the island of Madeira, which is near the coaft of Africa; befides, the voyage to Bermudas, added to the purity of the air, together with the abundance and quality of the fruits and vegetables, would probably restore all thofe to health, who are to be recovered either by good air or wholesome food. "But the reputation of thefe islands has fuffered from the report of the early navigators, who formerly vifited them in fmall veffels, and who were perhaps terrified by the occafional forms of thunder and lightning, and ftill more by the rocks and thoals with which they are said to be furrounded. The report of one or two timid or wonder-working travellers, at that early period, was probably fufficient to juftify the character given of thefe illands by our immortal Shakfpeare, who makes Ariel, in the Tempeft, tell Profpero, Safely in harbour Is the King's fhip; in the deep nook, where once • Thou call'dft me up at midnight to fetch dew From the ftill vex'd Bermoothes.' "Mr. Malone, in a note on this paffage, fays, Thus the islands now brown by the name of Bermudas, were frequently, though not always, called in our author's |