These observations were made in a season, when the waters rose rather higher than usual; so that we may take 31 feet for the mean

of the increase.

sons.

It must be observed, that the Ganges rises in a more considerable degree than the northern rivers that communicate with it, in the lower parts of its course (the Burrampooter excepted): and this is evident by the different circumstances that take place on the mixing of the waters of the Ganges and Teesta rivers, in the different seaThe Teesta is a large river which runs almost parallel to the Ganges, for near 150 miles. During the dry season, the waters of the Teesta run into those of the Ganges by two distinct channels, situated about twenty miles from each other: and a third channel at the same time discharges itself into the Megna. But during the season of the floods, the Ganges runs into the Teesta, whose outlet is then confined to the channel that communicates with the Megna. This alone is sufficient to shew how trifling the descent of these rivers must be, whose courses are thus regulated (not by the declivity of their beds, but) by their heights in respect to each other; which, like the flux and reflux of the tide, have the effect of giving contrary directions to the stream, at different seasons.

The inundation is nearly at a stand for some days preceding the middle of August, when it begins to run off; for although great quantities of rain fall in the flat countries, during August and September, yet, by a partial cefsation of the rains in the mountains, there happens a deficiency in the supplies necessary 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 August, and all September, from three to four inches; from September

have stated the middle of August for the period when the waters begin to run off; and in general it happens with as much regularity as the vicifsitudes of the seasons do. But there are exceptions to it; for in the year 1774 the rivers kept up for near a month after the usual time.

to the end of November, it gradually lefsens 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 a medium. These proportions must be understood to relate to such parts of the river as are removed from the influence of the tides; of which more will be said presently. 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 ceased, the remainder of the inundation goes off quickly by evaporation; leaving the lands highly manured, and in a state fit to receive the seed, after the simple operation of plowing.

There is a circumstance attending the increase of the Ganges, and which, I believe, is little known or attended to; because few people have made experiments on the heights, to which the periodical flood rises, in different places. The circumstance I allude to, is, the difference of the quantity of the increase (as expressed in the foregoing table) in places more or lefs remote from the sea. It is a fact, confirmed by repeated experiments, that from about the place where the tide commences, to the sea, 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 preserves the same level at all seasons (under similar circumstances of tide), and necefsarily influences the level of all the waters that communicate with it, unless precipitated in the form of a cataract. Could we suppose, for a moment, that the increased column of water, of 31 feet perpendicular, was continued all the way to the sea, by some preternatural agency: whenever that agency was removed, the head of the column would diffuse itself over the ocean, and the remaining part would follow, from as far back as the influence of the ocean extended; forming a slope, whose perpendicular height would be 31 feet. This is the precise state in which we find it. At the point of junction with the

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sea, the height is the same in both seasons, at equal times of the tide. At Luckipour, there is a difference of about six feet between the heights in the different seasons; at Dacca, and places adjacent, 14; and at Custee, 31 feet. Here then is a regular slope; for the distances between the places, bear a proportion to the respective heights. This slope must add to the rapidity of the stream; for, supposing the descent to have been originally four inches per mile, this will increase it to about five and a half. Custee is about 240 miles from the sea, by the course of the river; and the surface of the river there, during the dry season, is about 80 feet above the level of the sea at high water. * Thus far does the ocean manifest its dominion in both seasons: in the one by the ebbing and flowing of its tides; and in the other by depressing the periodical flood, till the surface of it coincides as nearly with its own, as the descent of the channel of the river will admit. †

Similar circumstances take place in the Jellinghy, Hoogly, and Burrampooter rivers; and, I suppose, in all others that are subject either to periodical, or occasional swellings.

Not only does the flood diminish near the sea, but the river banks diminish in the same proportion; so that in the dry season, 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 solution; which is, that the lownefs of the banks in places near the sea, is the true reason why the floods do not attain so considerable

*The tides in the river Amazons are perceptible at 600 miles above its mouth; but at an elevation of only 90 feet, according to M. DE CONDAMINE. It remains to be told what the state of the river was, at the time of making the experiment; because the land-floods have the effect of shortening the limits of the tide's way.

The Count DE BUFFON has slightly mentioned this circumstance attending the swelling of rivers; but imputes it to the increased velocity of the current, as the river approaches the sea: which, says he, carries off the inundation so quick, as to abate its height. Now (with the utmost deference to so great an authority) I could never perceive, that the current, either in the Ganges, or any other river, was stronger near the sea than at a distance from it. Even if we admit an acceleration of the current during the ebb-tide, the flux retards it in so considerable a degree, as at least to counterbalance the effects produced by the temporary increase of velocity.

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, diffuses itself over the surface of the country. In answer to this, I shall observe, that it is proved by experiment, that at any given time, the quantity of the increase in different places, bears a just proportion to the sum total of the increase in each place respectively: or, in other words, that when the river has risen three feet at Dacca, where the whole rising is about 14 feet; it will have rose upwards of six feet and a half at Custee, where it rises 31 feet in all.

The quantity of water discharged by the Ganges, in one second of time, during the dry season, is 80,000 cubic feet; but the river, when full, having thrice the volume of water in it, that it had at the time when the experiment was made; and its motion being also accelerated in the proportion of five to three; the quantity discharged in a second at that season is 405,000 cubic feet. If we take the medium the whole year through, it will be nearly 180,000 cubic feet in a second.

THE BURRAMPOOTER, which has its source from the opposite side of the same mountains that give rise to the Ganges, first takes its course eastward, or directly opposite to that of the Ganges, through the country of Thibet, where it is named Sanpoo or Zanciu, which bears the same interpretation as the Gonga of Hindoostan; namely, THE RIVER. The course of it through Thibet, as given by Father Du HALDE, and formed into a map by M. D'ANVILLE, though sufficiently exact for the purposes of general geography, is not particular enough to ascertain the precise length of its course. After winding with a rapid current through Thibet, it washes the

border of the territory of Lafsa (in which is the residence of the Grand Lama) and then deviating from an east to a south-east course, it approaches within 220 miles of Yunan, the westernmost province of China. Here it appears, as if undetermined whether to attempt a passage to the sea, by the gulf of Siam, or by that of Bengal; but seemingly determining on the latter, it turns suddenly to the west through Afsam, and enters Bengal on the north-east. I have not been able to learn the exact place where it changes its name; but as the people of Afsam call it Burrampoot, it would appear, that it takes this name on its entering Afsam. After its entry into Bengal, it makes a circuit round the western point of the Garrow mountains; and then, altering its course to south, it meets the Ganges about 40 miles from the sea.

Father Du HALDE exprefses his doubts concerning the course that the Sanpoo takes, after leaving Thibet; and only supposes generally, that it falls into the gulf of Bengal. M. D'ANVILLE, his geographer, not without reason, supposed the Sanpoo and Ava river to be the same; being justified by the information which his materials afforded him: for the Burrampooter was represented to him, as one of the inferior streams that contributed its waters to the Ganges, and not as its equal or superior; and this was sufficient to direct his researches, after the mouth of the Sanpoo river, to some other quarter. The Ava river, as well from its bulk, as the bent of its course for some hundred miles above its mouth, appeared to him to be a continuation of the river in question: and it was accordingly described as such in his maps, the authority of which was justly esteemed as decisive; and, till the year 1765, the Burrampooter, as a capital river, was unknown in Europe.

On tracing this river in 1765, I was no lefs surprised, at finding it rather larger than the Ganges, than at its course previous to its entering Bengal. This I found to be from the east; although all the former accounts represented it as from the north: and this un