In tracing the fea coaft of the delta, we find no lefs than eight openings; each of which, without hesitation, one pronounces to have been in its time the principal mouth of the Ganges. Nor is the occafional deviation of the principal branch, probably, the only cause of fluctuation in the dimenfions of the delta. One obferves that the deltas of moft capital rivers (the tropical ones particularly) encroach upon the fea. Now, is not this owing to the mud and fand brought down by the rivers, and gradually depofited, from the remoteft ages down to the present time? The rivers, we know, are loaded with mud and fand at their entrance into the fea; and we also know, that the fea recovers its tranfparency at the distance of twenty leagues from the coaft; which can only arife from the waters having precipitated their earthy particles within that space. The fand and mud banks at this time, extend twenty miles off fome of the islands in the mouths of the Ganges and Burrampooter; and rife in many places within a few feet of the surface. Some future generation will probably fee thefe banks rife above water, and fucceeding ones poffefs and cultivate them! Next to earthquakes, perhaps the floods of the tropical rivers produce the quickest alterations in the face of our globe. Extenfive islands are formed in the channel of the Ganges, during an interval far short of that of a man's life; fo that the whole process is completed in a period that falls within the compass of his obfervation *. Some of these islands, four or five miles in extent, are formed at the angular turnings of the river, and were originally large fand banks thrown up round the points (in the manner before described) but afterwards infulated by breaches of the river. Others are formed in the straight parts of the river, and in the middle of the stream; and owe their origin to some obstruction lurking at the bottom. Whether this be the fragments of the river bank; a large tree, fwept down from it; or

Accordingly, the laws respecting alluvion are ascertained with great precision.

a funken

a funken boat; it is fufficient for a foundation: and a heap of fand is quickly collected below it. This accumulates amazingly fast: in the courfe of a few years it peeps above water, and having now ufurped a confiderable portion of the channel, the river borrows on each fide to fupply the deficiency in its bed; and in such parts of the river we always find steep banks on both fides *. Each periodical flood brings an addition of matter to this growing ifland; increafing it in height as well as extenfion, until its top is perfectly on a level with the banks that include it: and at that period of its growth it has mould enough on it for the purposes of cultivation, which is owing to the mud left on it when the waters fubfide, and is indeed a part of the economy which nature obferves in fertilizing the lands in general.

While the river is forming new iflands in one part, it is fweeping away old ones in other parts. In the progrefs of this deftructive operation, we have opportunities of obferving, by means of the fections of the falling bank, the regular diftribution of the feveral : ftrata of fand and earths, lying above one another in the order in which they decrease in gravity. As they can only owe this difpofition to the agency of the stream that deposited them, it would appear, that these substances are fufpended at different heights in the stream, according to their respective gravities. We never find a. ftratum of earth under one of fand; for the muddy particles float: nearest the surface. I have counted feven diftinct ftrata in a section of one of these iflands. Indeed, not only the islands, but most of the river banks wear the fame appearance: for as the river is always changing its prefent bed,, and verging towards the fite of fome former one now obliterated, this must neceffarily be the cafe.

This evidently points out the means for preventing encroachments on a river bank in the ftraight parts of its courfe, viz. to remove the fhallows that accumulate in the middle of its

channel.

+ A glass of water taken out of the Ganges, when at its height, yields about one part in four of mud. No wonder then that the fubfiding waters fhould quickly form a ftratum of earth; or that the delta should encroach upon the fea!

As a strong prefumptive proof of the wandering of the Ganges from the one fide of the delta to the other, I muft obferve, that there is no appearance of virgin earth between the Tiperah Hills on the east, and the province of Burdwan on the west; nor on the north till we arrive at Dacca and Bauleah. In all the sections of the numerous creeks and rivers in the delta, nothing appears but fand and black mould in regular ftrata, till we arrive at the clay that forms the lower part of their beds. There is not any substance fo coarfe as gravel either in the delta or nearer the fea than 400 miles*, where a rocky point, a part of the base of the neighbouring hills, projects into the river: but out of the vicinity of the great rivers the foil is either red, yellow, or of a deep brown.

I come now to the particulars of the annual swelling and overflowing of the Ganges †.

It appears to owe its increafe as much to the rain water that falls in the mountains contiguous to its fource, and to the fources of the great northern rivers that fall into it, as to that which falls in the plains of Hindooftan; for it rifes fifteen feet and a half out of thirty-two (the fum total of its rifing) by the latter end of June: and it is well known, that the rainy feafon does not begin in most of the flat countries till about that time. In the mountains it begins early in April; and by the latter end of that month, when the rain water has reached Bengal, the rivers begin to rife, though by very flow degrees; for the increase is only about an inch per

At Oudanulla.

An opinion has long prevailed, that the fwelling of the Ganges, previous to the commencement of the rainy feafon in the flat countries, is in a great measure owing to the melting of the fnow in the mountains. I will not go fo far as totally to difallow the fact; but can by no means fuppofe, that the quantity of fnow water bears any proportion to the increase of the river.

The vast collection of vapours, wafted from the fea by the foutherly or fouth-west monfoon, are fuddenly stopped by the lofty ridge of mountains that runs from east to weft through Thibet. It is obvious, that the accumulation and condenfation of thefe vapours, must first happen in the neighbourhood of the obftacle; and fucceflively in places more remote, as fresh fupplies arrive to fill the atmosphere. Hence the priority of commencement of the rainy feafon in places that lie nearest the mountains.

day

day for the first fortnight. It then gradually augments to two and three inches before any quantity of rain falls in the flat countrics; and when the rain becomes general, the increase on a medium is five inches per day. By the latter end of July all the lower parts of Bengal, contiguous to the Ganges and Burrampooter, are overflowed, and form an inundation of more than a hundred miles in width; nothing appearing but villages and trees, excepting very rarely the top of an elevated fpot (the artificial mound of fome deferted village) appearing like an island.

The inundations in Bengal differ from thofe in Egypt in this particular, that the Nile owes its floods entirely to the rain-water that falls in the mountains near its fource; but the inundations in Bengal are as much occafioned by the rain that falls there, as by the waters of the Ganges; and as a proof of it, the lands in general are overflowed to a confiderable height long before the bed of the river is filled. It must be remarked, that the ground adjacent to the river bank, to the extent of fome miles, is confiderably higher than the rest of the country*, and ferves to feparate the waters of the inundation from those of the river until it overflows. This high ground is in fome feafons covered a foot or more; but the height of the inundation within, varies, of courfe, according to the irregularities of the ground, and is in fome places twelve feet.

Even when the inundation becomes general, the river ftill fhews itself, as well by the grafs and reeds on its banks, as by its rapid and muddy ftream; for the water of the inundation acquires a blackish

All the rivers that are fituated within the limits of the monfoons, or fhifting trade winds, are fubject to overflowings at annually stated periods, like the Ganges: and thefe periods return during the feafon of the wind that brings vapours from the fea (which in Bengal, &c. is the foutherly one) and this being periodical, the falls of rain must neceffarily be fo too.

The northerly wind, which blows only over the land, is dry; for no rain (except cafual fhowers) falls during the continuance of that monfoon.

This property of the bank is well accounted for by Count BUFFON, who imputes it to the precipitation of mud made by the waters of the river, when it overflows. The inundation, fays he, purifies itfelf as it flows over the plain; fo that the precipitation must be greatest on the parts nearest to the margin of the river.

hue,

hue, by having been fo long ftagnant among grafs and other vegetables: nor does it ever lofe this tinge, which is a proof of the predominancy of the rain water over that of the river; as the flow rate of motion of the inundation (which does not exceed half a mile hour) is of the remarkable flatnefs of the country.

per

There are particular tracts of lands, which, from the nature of their culture, and species of productions, requires less moisture than others; and yet, by the lownefs of their fituation would remain too long inundated, were they not guarded by dikes or dams, from fo copious an inundation as would otherwise happen, from the great elevation of the furface of the river above them. Thefe dikes are kept up at an enormous expence; and yet do not always fucceed,. for want of tenacity in the foil of which they are compofed. It is calculated that the length of thefe dikes collectively, amounts to more than a 1000 English miles. Some of them, at the bafe, are equal to the thickness of an ordinary rampart. One particular branch of the Ganges, (navigable only during the rainy feafon,. but then equal to the Thames at Chelsea) is conducted between two of these dikes, for about 70 miles: and when full, the paffengersin the boats, look down on the adjacent country, as from an

eminence.

During the swoln state of the river, the tide totally loses its effect of counteracting the stream; and in a great measure that of ebbing and flowing, except very near the fea. It is not uncommon for a ftrong wind, that blows up the river for any continuance, to fwell the waters two feet above the ordinary level at that feafon and fuch accidents have occafioned the lofs of whole crops of rice *. A very tragical event happened at Luckipour † in 1763, by a strong

* The rice I fpeak of is of a particular kind; for the growth of its ftalk keeps pace with the increase of the flood at ordinary times, but is deftroyed by a too fudden rife of the water. The harvest is often reaped in boats. There is alfo a kind of grafs which overtops the flood in the fame manner, and at a small distance has the appearance of a field of the richest verdure.

About fifty miles from the fea.

gale