main 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.

During the fwoln ftate of the river, the tide totally lofes its effect of counteracting the ftream; and in a great ineafure that of ebbing and flowing, except very near the fea. It is not uncommon for a strong wind, that blows up the river for any continuance, to fwell, the waters two feet above the ordinary level at that season and fuch accidents have occafioned the lofs of whole crops of rice. A very tragical event happened at Luckipour in 1763, by a strong gale of wind confpiring with a high fpring tide, at a feafon when the periodical flood was within a foot and a half of its highest pitch. It is faid that the waters rofe fix feet above the ordinary level. Certain it is, that the inhabitants of a confiderable diftrict, with their houses and cattle, were totally fwept away; and, to aggravate their diftrefs, it happened in a part of the country which fcarce produces a fingle tree for a drowning man to escape to.

Embarkations of every kind traverse the inundation: those bound upwards, availing themfelves of a direct courfe and ftill water, at a feafon when every ftream rushes like a torrent. The wind too, which at this feafon blows regularly from the foutheaft, favours their progrefs; info.

much, that a voyage, which taket up nine or ten days by the courfe of the river when confined within its banks, is now effected in fix. Hufbandry and grazing are both fufpended; and the peafant traverfes in his boat, thofe fields which in another feafon he was wont to plow; happy that the elevated fite of the river banks place the herbage they contain; within his reach, otherwife his cattle muft perish.

The following is a table of the gradual increafe of the Ganges and its branches, according to obfervations made at Jellinghy and Dacca.

Thefe obfervations were made in a season, when the waters rose rather higher than ufual; fo that we may take 31 feet for the medi um of the increase.

The inundation is nearly at a ftand for fome days preceding the middle of Auguft, when it begins to run off; for although great quantities of rain fall in the flat countries, during Auguft and September, yet, by a partial ceffation of the rains in the mountains, there happens a deficency in the fupplies neceffary to keep up the inundation. The quantity of the daily decrease of the river is nearly in the following proportion: during the latter half of Auguft, and all September, from three to four inches; from September to the

end

end of November, it gradually leffens from three inches to an inch and a half; and from November to the latter end of April, it is only half an inch per day at á medium. Thefe proportions muft be understood to relate to fuch parts of the river as are removed from the influence of the tides; of which more will be faid by and by. The decrease of the inundation does not always keep pace with that of the river, by reason of the height of the banks; but after the beginning of October, when the rain has nearly ceafed, the remainder of the inundation goes off quickly by evaporation, leaving the lands highly manured, and in a ftate fit to receive the feed, after the fimple operation of plowing.

There is a circumftance attending the increase of the Ganges, and which, I believe, is little known or attended to; becaufe few people have made experiments on the heights to which the periodi cal flood rifes in different places. The circumftance I allude to, is, the difference of the quantity of the increafe (as expreffed in the foregoing table) in places more or lefs remote from the fea. It is a fact, confirmed by repeated experiments, that from about the place where the tide commences, to the fea, the height of the periodical increase diminishes gradually, until it totally disappears at the point of confluence. Indeed, this is perfectly conformable to the known laws of fluids: the ocean preferves the fame level at all feafons (under fimilar circumftances of tide) and neceffarily influences the level of all the waters that communicate with it, unless precipitated in the VOL. XXIV.

form of a cataract. Could we fuppofe, for a moment, that the increafed column of water, of zi feet perpendicular, was continued all the way to the fea, by fome preternatural agency: whenever that agency was removed, the head of the column would diffuse itself over the ocean, and the remaining parts would follow, from as far back as the influence of the ocean extended; forming a flope, whofe perpendicular height would be 31 feet. This is the precife ftate in which we find it. At the point of junction with the fea, the height is the fame in both feasons at equal times of the tide. At Luckipour there is a difference of about fix feet between the heights in the different feafons; at Dacca, and places adjacent, 14; and near Custee, 31 feet. Here then is a regular flope; for the diftances between the places bear a proportion to the refpective heights. This flope must add to the rapidity of the ftream; for, fuppofing the defcent to have been originally four inches per mile, this will increafe it to about five and an half. Cuftee is about 240 miles from the fea, by the course of the river; and the furface of the river there, during the dry feafon, is about 80 feet above the level of the fea at high water. Thus far does the ocean manifeft its dominion in both feafons in the one by the ebbing and flowing of its tides; and in the other by depreffing the periodical flood, till the furface of it coincides as nearly with its own, as the descent of the channel of the river will admit.

Similar circumftances take place in the Jellinghy, Hoogly, and

E

Burram

Burrampooter Rivers; and, I fuppofe, in all others that are subject either to periodical or occafional fwellings.

Not only does the flood diminifh near the fea, but the river banks diminish in the fame proportion; fo that in the dry feafon the height of the periodical flood may be known by that of the bank.

I am aware of an objection that may be made to the above folution; which is, that the lownefs of the banks in places near the fea, is the true reafon why the floods do not attain fo confiderable a height, as in places farther removed from it, and where the banks are high; for that the river, wanting a bank to confine it, dif. fufes itself over the furface of the country. In anfwer to this, I shall obferve, that it is proved by experiment, that at any given time, the quantity of the increase in different places, bears a juit proportion to the fum total of the increafe in each place refpectively: or, in other words, that when the river has rifen three feet at Dacca, where the whole rifing is about 14 feet; it will have rifen upwards of fix feet and a half at Cuftee, where it rifes 31 feet in all.

The quantity of water difcharged by the Ganges, in one fecond of time, during the dry feafon, is 80,000 cubic feet; but in the place where the experiment was made, the river, when full, has thrice the volume of water in it; and its motion is alfo accelerated in the proportion of 5 to 3: fo that the quantity difcharged in a fecond at that feafon is 405,000 cubic feet. If we take the medi

um the whole year through, it will be nearly 180,000 cubic feet in a fecond.

THE Burrampooter, which has its fource from the oppofite fide of the fame mountains that give rife to the Ganges, first takes its courfe eastward (or directly oppofite to that of the Ganges) through the country of Thibet, where it is named Sanpoo or Zanciu, which bears the fame interpretation as the Gonga of Hindooftan : namely, the River. The course of it through Thibet, as given by Father Du Halde, and formed into a map by Mr. D'Anville, though fufficiently exact for the purpofes of general geography, is not particular enough to afcertain. the precife length of its courfe. After winding with a rapid current through Thibet, it washes the border of the territory of Laffa (in which is the refidence of the grand Lama) and then deviating from an eaft to a fouth-eaft course, it approaches within 220 miles of Yunan, the westernmost province of China. Here it appears, as if undetermined whether to attempt a paffage to the fea by the Gulf of Siam, or by that of Bengal; but feemingly determining on the latter, it turns fuddenly to the weft through Affam, and enters Bengal on the north-eaft. I have not been able to learn the exact place where it changes its name; but as the people of Aflam call it Burrampoot, it would appear, that it takes this name on its entering Affam. After its entry into Bengal, it makes a circuit round the western point of the Garrow Mountains; and then,

altering

Father Du Halde expreffes his doubts concerning the courfe that the Sanpoo takes after leaving Thibet, and only fuppofes generally that it falls into the gulf of Bengal. M. D'Anville, his geographer, with great reafon fuppofed the Sanpoo and Ava River to be the fame and in this he was juftified by the information which his materials afforded him: for the Burrampooter was reprefented to him, as one of the inferior streams that contributed its waters to the Ganges, and not as its equal or fuperior; and this was fufficient to direct his researches, after the mouth of the Sanpoo River, to fome other quarter. The Ava River, as well from its bulk, as the bent of its courfe for fome hundred miles above its mouth, appeared to him to be a continuation of the river in queftion and it was accordingly defcribed as fuch in his maps, the authority of which was justly efteemed as decifive; and, till the year 1765, the Burrampooter, as a capital river, was unknown in Europe.

On tracing this river in 1765, I was no less furprized, at finding it rather larger than the Ganges, than at its courfe previous to its entering Bengal. This I found to be from the eaft; although all the former accounts reprefented it as from the north: and this unexpected discovery foon led to enquiries, which furnished me with an account of its general courfe to within a hundred miles of the place where Du Halde left the Sanpoo. I could no longer doubt,

:

were one and the fame river and to this was added the positive assurances of the Affamers, "That their river came from the Northweft, through the Bootan mountains." And to place it beyond a doubt, that the Sanpoo River is not the fame with the river of Ava, but that this last is the great Nou Kian of Yunan; I have in my poffeffion a manufcript draught of the Ava River, to within 150 miles of the place where Du Halde leaves the Nou Kian, in its courfe towards Ava; together with very authentic information that this river (named Irabattey by the people of Ava) is navigable from the city of Ava into the province of Yunan in China.

The

The Burrampooter, during a courfe of 400 miles through Bengal, bears fo intimate a refemblance to the Ganges, except in one particular, that one defcription may ferve' for both. exception I mean is, that, during the laft 60 miles before its junction with the Ganges, it forms a stream which is regularly from four to five miles wide, and but for its frethness might pass for an arm of the fea. Common defcription fails in an attempt to convey an adequate idea of the grandeur of this magnificent object; for,

-Scarce the mufe Dares ftretch her wing o'er this enormous mafs

Of rushing water; to whofe dread expanfe, Continuous depth, and wond'rous length of course,

I have already endeavoured to account for the fingular breadth of the Megna, by fuppofing that the Ganges once joined it where the Iflamutty now does; and that their joint waters fcooped out its prefent bed. The prefent junction of these two mighty rivers below Luckipour, produces a body of running fresh water, hardly to be equalled in the old hemifphere, and, perhaps, not exceeded in the new. It now forms a gulf interfperfed with iflands, fome of which rival, in fize and fertility, our Ifle of Wight. The water at ordinary times is hardly brackish at the extremities of these islands; and, in the rainy feafon, the fea (or at least the furface of it) is perfectly fresh to the distance of many leagues out.

The Bore (which is known to be a fudden and abrupt influx of the tide into a river or narrow frait) prevails in the principal branches of the Ganges, and in the Megna; but the Hoogly Ri ver, and the paffages between the ilands and fands fituated in the gulf, formed by the confluence of the Ganges and Megna, are more fubject to it than the other rivers. This may be owing partly, o their having greater embouchures in proportion to their channels,

Town; and fo quick is its motion, that it hardly employs four hours in travelling from one to the other, although the diftance is near 70 miles. At Calcutta, it fometimes occafions an inftantaneous rife of five feet: and both here, and in every other part of its track, the boats, on its approach, immediately quit the fhore, and make for fafety to the middle of the river.

In the channels, between the iflands in the mouth of the Megna, &c. the height of the Bore is faid to exceed twelve feet; and is fo terrific in its appearance, and dangerous in its confequences, that no boat will venture to pafs at fpring tide. After the tide is fairly paft the iflands, no veftige of a Bore is feen, which may be owing to the great width of the Megna, in comparifon with the paffages between the islands; but the effects of it are visible enough by the fudden rifing of the tides

of the Air that has been supposed to come through the Pores of the Skin, and of the Effects of the Perfpiration of the Body; from Priestley's Experiments in Natural Philofophy.

HAVE fometimes found it ne

means a larger proportion of tide is forced through a paffage comparatively smaller; and partly, to there being no capital openings near them, to draw off any confiderable portion of the accumulating tide. In the Hoogly or Calcutta River, the Bore commences at Hoogly point (the place where the river first contracts itfelf) and is perceptible above Hoogly

means agreeable to me, to correct the mistakes of others on the fubject of which I am treating; and I must appropriate this fection to that bufinefs.

It cannot be thought extraordinary, that when it has been imagined that air is extracted from the most compact bodies, as gold, by means of the air pump, it should be thought to iffue from the hu

man