E. On the contrary, when he is in Capricorn the N. E. perennial extends an equal number of degrees to the south of the equator, but it inclines more to the northward. All which facts clearly prove, that the lower current of air, being rarefied by the reflected heat of the sun, ascends, and the equilibrium is restored by a large body of dense air, which rushes forward in a right line, and with a strong current, to fill up the vacuum.

The early Portuguese and other European navigators, in attempting to sail towards the Cape of Good Hope, were greatly obstructed in their voyages thither by not adverting to these circumstances: but the use of the compass was then very little known. Most of them therefore endeavoured to keep close to the west coast of Africa, by which means, being then also ignorant of the real geography of this continent, they expected to shorten their distance; but thus situated, they necessarily encountered constant calms and tornadoes, and seldom performed their voyage out and home in less than two or three years: whilst some other adventurers, nearly about the same period, in trying to avoid these inconveniences, fell in with the American coast, and were likewise detained by the S. E. wind, which of course retarded their progress on that side, for they could not without great difficulty, and that only at particular seasons, make their way to the southward.

But the better informed modern navigators, profiting by long and dear-bought experience, have learned to keep nearly the mid-channel, where they are assisted by constant perennial winds, and where they may yet allow some room for leeway in the southern tropic, a precaution particularly necessary whilst the sun is near our summer solstice, for at that time the S.E. perennial wind in. clines very much towards the southward. Both outward and home. ward bound India ships pass the equator in the Atlantic in about 18 or 20 degrees W. By keeping this course they never fall in with the coast of America, either going to the Cape of Good Hope, or returning from it; and at the same time they avoid the calms on the coast of Africa.

After having passed the southern tropic three or four degrees, ships which sail from Europe between February and May seldom find themselves more than 26 or 28 degrees W.; which by the trenching away of the American coast to the westward in these la. titudes, is about half-way between the two continents. The winds

VOL. IV.

in these latitudes, in the month of May, are generally found va riable, as if alternately and equally attracted by both continents; but as vessels advance to the southward in the months of May and June, and approach towards Africa, the wind between the latitude of 28 and 35 degrees S. comes round to the westward, and generally blows fresh from the N.W. until they have passed the Cape of Good Hope.

The wind just beyond the bounds of the perennial coming from this quarter, seems in some degree to confirm Dr. Halley's theory of the superior current of air in this situation forming a contrary current at the commencement of the temperate zone. This obser vation must be confined to particular seasons within certain limits, - and not be considered as invariably the case, even in the southern Atlantic; for in those same parallels of latitude, the winds are light and variable, coming often from the S. E. and veering occasionally to almost every point of the compass. To the eastward of the Cape the S.E. wind blows frequently during their winter with considerable violence for several days successively. But the southerly winds to the eastward of the Cape blow with most violence when the sun is in Capricorn, that is during their summer months; for when the land on the extremity of the east coast of Africa is heated by the presence of the sun, the colder air from the antarctic circle, put in motion by the sun's melting the ice in those frozen regions, frequently rushes forward towards the land near the Cape of Good Hope with considerable force.

Bacon long since, and even Pliny before him, has in effect observed, that, from the vicinity of lofty mountains covered with snow, the winds blow periodically when the snow begins to melt. Ubicunque siti sunt montes alli et nivales, ab ea parte flant venti stati ad tempus quo nives solvuntur.

The S.E. perennial wind blows constantly some few degrees to the eastward of Madagascar at all seasons of the year, as far nearly as the island of Java, where it comes within the reach of the regular monsoon; and indeed between the island of Madagascar and the main land of Africa, commonly called the Mosambique Channel, the perennial winds are checked by the proximity of the two great bodies of land, and consequently partake of the nature of mon

soons.

[Capper on Winds and Monsoors.

SECTION IV.

Periodical Winds.

Tropical Sea-winds or Monsoons.

THE name as well as the nature of the monsoons is misunder. stood; the word is not derived from the name of a great mariner, but clearly from the Persian word mousum, meaning season. In tropical countries there are but two seasons: those in Hindustan are distinguised by the N.E. and S.W. monsoons. But farther to the eastward and southward of the line, and the gulf of Bengal, the monsoons blow from different quarters. The N. E. becomes in those parts the N.W. and the S.W. becomes the S.E. The causes of those changes and the original causes of the monsoons I shall here. after attempt to explain, but first I shall endeavour to point out some generally prevailing errors respecting the course and changes of them in different parts of Hindustan, derived in all probability from the early navigators to India. As neither ancient nor modern geographers have yet fixed, with any degree of precision, the names or boundaries of the different oceans, seas, and gulfs where the monsoons prevail, to avoid further interruption and trouble I shall beg leave in this place to make a new division of them.

The gulf of Bengal is apparently so called on account of the rich and fertile province of that name, situated at the north, or head of it. In this gulf therefore no alteration is proposed. The S.W. boundaries of this gulf I shall fix at Dondre Head, on the island of Ceylon, latitude 5° 50′ N. and longitude 80° 48′ E. of Greenwich. And for the S.E. side, Acheen Head, latitude 5° 30′ N. longitude 95°30′ E. For the northern extremity, the well known city of Calcutta, latitude 22° 34′ 45′′ N. longitude 88° 29′ 30" E. On the W. side of the peninsula, the coast of Malabar, with Cape Guardafui, on the coast of Africa, forms another considerable gulf, frequently called the Arabian, but generally the Indian Sea: but this latter in particular seems to be a name equally applicable, and often applied to the gulf of Bengal, and even to the seas to the eastward and southward, and consequently is very indefinite; whilst the Arabian Sea may be confounded with the Red Sea or Arabian Gulf.

Adopting therefore in a great measure the plan of the oriental geographers, I shall name this sea the Gulf of Sind. The river Indas giving the name to the first, and Hindustan divided by the Ganges to the second division. The river Indus will then be placed at the head of one bay, and the Ganges at the head of the other; Tatta, a considerable city, situated on the former, and Calcutta on the latter. Tatta, according to Major Rennel, is in the latitude of 24° 50′ N. longitude, 67° 37′ E. Cape Guardafui to the S. W. latitude 12 degrees N. longitude 52° 30′ E. and Cape Comorin to the S.E. in the latitude of 7° 56′ N. longitude 78° 5' E.

From the southern extremity of these two gulfs to the tropic of Capricorn, extending likewise eastward from the east coast of Africa to the west side of New Holland, I shall denominate the Indian Ocean, this being a considerable portion of the ocean leading to both gulfs in India, as well as to China and the eastern islands, including all India, both within and without the Ganges. From that parallel of latitude to the south pole, including that part of the ocean situated between the E. of Africa and the W. of New Hol land, I shall call the Great Southern Ocean. These new divisions may not, perhaps, be deemed in every respect strictly accurate, but they will answer our purpose, and therefore, without further preface, we will now proceed to make some observations on the different monsoons and prevailing winds within these boundaries.

The winds in the gulf of Bengal are generally said to blow six This is far months from the N. E. and the other six from the S.W. from being precisely true respecting any part of India; it is, how. ever, sufficiently accurate for our present purpose, and therefore I shall in part adopt this position as well as the common country name of monsoon; trusting, that in the course of this enquiry, I shall be able to account for the several deviations of the wind from the monsoon points, and at the same time in some measure to explain the causes of them.

From the island of Ceylon to Balasore Roads, the N.E. monsoon is said to begin, near the coast of Coromandel, early in October. But in fact between the two monsoons, the expiration of the one and the commencement of the other, the winds and currents are variable on this coast, partaking of both; frequently, however, cans prevail during the whole month of September, and even early

in October, with a strong current from the N. E. towards the S. W. At this period we must remember that the sun is fast approaching towards the equinoctial, which he crosses nearly about the 22d of September. As his declination afterwards increases from seven to fifteen degrees S. which is between the 10th and 31st of October, his absence from the northern hemisphere begins to be felt; and as he at the same time rarefies the air both by sea and land to the southward of the equator, the warm air then over the Indian Ocean, but particularly over the eastern side of the continent of Africa, as usual ascends, and the cold air from the N. meeting the perennial east wind, they pass forward progressively, beginning where the rarefaction takes place, and probably continuing to an immense distance, and thus form the N.E. monsoon. The exact point where the northerly wind terminates I shall not, in this place, at. tempt to ascertain; but we may venture to suppose, that it must be at least as far towards the N.E. as the west side of the Thibet and Napal mountains, separating India from China, and which in winter are always covered with snow. From this frozen eminence a current of cold air will move with considerable velocity towards the tropic, on the approach of the sun, until the equilibrium is restored; but at the latter end of January, the sun again beginning to return towards the N. produces a sensible effect on the air; for in proportion as he approaches towards the equator, the current of air in the gulf of Bengal, near the land, takes a different direction. About this time the wind, immediately on the coast of Coromandel, no longer blows violently or regularly from the N.E. as in the commencement of the monsoon, but first abates in strength (like a current of water when the level is nearly restored) and then changes daily to regular land and sea breezes, which of course, near the coast, are obviously occasioned by the alternate rarefaction of the air by sea and land.

In the Mosambique Channel the monsoons correspond nearly with those on the Malabar coast, if not in their commencement at least in their duration. The S. W. monsoon begins in April and continues till November. The N.E. then succeeds, and continues until April; but the S.W. monsoon in this channel is the fair sea. son, and the wind varies sometimes towards the S. E. and E.S.E. on either coast, about the middle of November, where also there