THE stream of all rivers is more rapid in proportion as the channel diminished; for instance, it will be much swifter where it is ten yards broad, than where it is twenty; for the force behind still pushing the water for ward, when it comes to the narrow part, it must make up by velocity what it wants in room.

It might be supposed, that bridges and other obstacles in the current of a river would retard its velocity. But the difference they make is very inconsiderable. The water, by these stoppages, gets an elevation above the object, which, when it has surmounted, it gives a velocity that recompences the former delay. Islands and turnings also retard the stream but very inconsiderably.

Any cause which diminishes the quantity of the water, most sensibly diminishes the force and velocity of the stream. An increase of water in the bed of a river always increases its velocity-except in cases of inundation. The instant the river has overflowed its banks, the rapidity of its current is always turned that way, and the inundation is seen to continue for some days, which it would not do, if, as soon as the cause was discontinued, it acquired its former rapidity.

A violent wind, that sets directly up against the course of a stream, will always retard, and sometimes intirely stop, its course. There have been instances of this, when the bed of a large river has been left nearly dry for some hours, and fish have been caught among the stones at the bottom.

A little river may be received into a large one without augmenting either its width or depth. This, at first view, seems a paradox; yet it is very easily accounted for. The little river, in this case, only goes towards increasing the swiftness of the larger, and putting its dormant VOL. IV.

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waters into motion. In this manner, the Venetian branch of the Po is pushed on by the Fararese branch and that of Panaro, without any enlargement of its breadth or depth from these accessions.

A river tending to enter another, either perpendicularly, or in an opposite direction, will be diverted, by degrees, from that direction, and be obliged to make itself a more favourable entrance downward, and more conspiring with the stream of the former. The union of two rivers into one, makes it flow the swifter; since the same quantity of water, instead of rubbing against four shores, now only rubs against two. And besides, the current being deeper, becomes, of course, more fitted for motion.

Rivers form one of the chief features of the surface of this globe, serving as voiders of all that is immediately redundant in our rains and - springs, and also as boundaries and barriers betwixt nations, and even as highways, and in many countries as plentiful storehouses. They also fertilize our fields by their waters, by bringing from the mountains the mould which they wash down in their course.

Before we begin to describe some of the largest rivers in the world, we will present to our readers the following figurative and pleasing description of a river, written by an ancient author. "The river (says he) bears some resemblance to the life of man; it springs from the earth, but its origin is in heaven. Its beginnings are insignificant,, and its infancy is frivolous; it plays among the flowers of a meadow: it waters a garden, or turns a mill. Gathering strength in its youth, it becomes wild and impetuous. Impatient of the restraints which it still meets with in the hollows among the mountains, it is restless and fretful; quick in its turnings and unsteady in its course. Now it is a roaring cataract, tearing up and overturning whatever opposes its progress, and it shoots headlong from a rock; then it becomes a sullen and gloomy pool, buried in the bottom of a glin. Recovering breath by repose, it again dashes along, till tired of the uproar and mischief, it quits all that it has swept before it, and leaves the opening of the valley strewed with the rejected waste. Now, quitting its retirement, it comes abroad into the world, journeying, with more prudence and discretion, through cultivated fields, yielding to circumstances, and winding round what would trouble it to overwhelm or remove. It passes through populous cities, and all the busy haunts of men, tendering its services on every side, and becomes the blessing and ornament of the country. Now increased by numerous alliances, and advanced in its course of existence, it becomes grave and stately in its motions, loves peace and quiet, and in majestic silence rolls on its mighty waters, till it is laid to rest in the vast abyss."

The course of rivers gives us the best general method for judging of the elevation of countries. Thus is appears that Savoy and Switzerland are the highest parts in Europe, from whence the ground slopes in every direction. From the Alps proceed the Danube and the Rhine, whose courses mark the two great vallies, into which many lateral streams descend. The Po also, and the Rhone, come from the same head, and with a steeper and shorter course, find their way to the sea through

vallies of less breadth and length. On the west side of the vallies of the Rhine and the Rhone, the ground rises pretty fast, so that few tributary streams come into them on that side; and from this gentle elevation France slopes to the westward. If a line nearly straight, but bending a little to the northward, be drawn from the head of Savoy and Switzerland, all the way to Solikamskay, in Siberia, it will nearly pass through the most elevated part of Europe; for in this track most of the rivers have their rise. On the left go off the various feeders of the Elbe, the Oder, the Wesel, the Niemen, the Duna, the Neva, the Dwina, and the Petzora. On the right, after passing the feeders of the Danube, we see the sources of the Sereth and the Pruth, the Dneister, the Bog, the Dnieper, the Don, and the mighty Wolga with his seventy mouths. The elevation, however, is extremely moderate; and it appears, from the levels taken with the barometer by the Abbe Chappe d'Auteroche, that the head of the Wolga is not more than four hundred and seventy feet above the surface of the Caspian, into which it runs, though the course of that river, from Reschow to Astracan, is six hundred and fifty leagues. Spain and Portugal, on the one hand, and the whole of Scandinavia on the other, form two detached parts of Europe, which have little symmetry with the rest.

A chain of mountains begins in Nova Zembla, and stretches due south till it comes near to the Caspian Sea, dividing Europe from Asia. About three or four degrees north of the Caspian, it bends to the south east, traverses western Tartary, and passing between the Zengis and Zaizan lakes, it then branches to the east and south. The eastern branch runs to the shores of Korea and Kamtschatka. The southern branch traverses Turkestan and Thibet, separating them from India, and at the head of the kingdom of Ava joins an arm stretching from the great eastern branch, and here forms the centre of a very singular radiation. Chains of mountains issue from it in every direction: : three or four of them keep very close together, dividing the continent into narrow slips, which have each a large river flowing in the midst, and reaching to the extreme points of Malacca, Cambodia, and Cochin China.

From the same central point proceeds another great ridge due east, and passes a little north of Canton in China.

We called this a singular centre: for though it sends off so many branches, it is by no means the most elevated part of the continent.-In the triangle which is included between the first southern ridge, (which comes from between the lakes Tanges and Zaizan) the great eastean ridge and its branch, which almost unites with the southern ridge, li the Boutan, and part of Thibet, and the many little rivers which occupy its surface, flow southward and eastward, uniting a little to the north of the centre before mentioned, and then pass through a gorge eastward into China.

And it is further observable, that these great ridges do not appear to be seated on the highest parts of the country; for the rivers which correspond to them are at no great distance from them, and receive

their greatest supplies from the other sides. This is remarkably the case with the great river Oby, which is almost parallel to the ridge from the lakes to Nova Zembla. It receives its supplies from the east, and indeed it has its source far east.

The highest grounds of the continent, (if we except the ridges, which are boundaries) seem to be in the country of the Calmucks, about 95 degrees east from London, and about latitude 45 north. It is represented as a fine though sandy country, having many little rivers which lose themselves in the sand, or else end in little salt lakes.

This elevation stretches north-east to a great distance; and in this track we find the heads of the Irtish, Selenga, and Zunguskaia; these are the chief tributaries to the Oby.

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Here we find also the Olenitz, the Lena, the Yena, and some other rivers, which all go off to the north. On the other side we have the great river Amur, which is the boundary betwixt Russian and Chinese Tartary; there are also many other rivers, with whose names not familiar. The Hoangho, a great river of China, rises on the southern side of the great eastern ridge, which we have so often mentioned. This elevation, which is a continuation of the former, is somewhat of the same complexion, being very sandy, and at present is a desert of prodigious extent. It is described, however, as interspersed with vast tracts of rich pasture; and it is certain that it was formerly the residence of a powerful clan of Tartars, who migrated southward, and became known by the name of Turks, who in time possessed several of the richest kingdoms of Asia.

In the south-western extremity of this vast country are found remains not only of barbaric magnificence, but even of cultivation and elegance. The country now belongs to Russia; and it was a profitable privilege granted by Peter the Great to some adventurers to search these sandy deserts for the remains of foriner opulence; and many pieces of delicate workmanship, (though not in a stile which we should admire) in gold and silver were found. Vaults also were discovered, buried in sand, filled with papers in a character wholly unknown: and a wall was discovered, extending several miles, built with hewn stone, and ornamented with corniche and battlements. But we must return to our subject.

A great ridge of mountains begins at the south-east corner of the Black Sea, and proceeds eastward, ranging along the south side of the Caspian, and, still advancing, unites with the mountains first mentioned in Thibet, sending off some branches to the south, which divide Persia India, and Thibet. From the south side of this ridge flow the Euphrates, the Tigris, the Indus, the Ganges, &c. and from the north the ancient Oxus, and many other unknown streams.

There is a remarkable circumstance in this quarter of the globe.Although it seems to be nearest to the greatest elevation, it seems also to have places of great depression. The Caspian Sea is lower than the ocean. There is in its neighbourhood another great bason of salt water, the lake Aral, which receives the waters of the Oxus, which is said to be the ancient Gihon, and is supposed to have once run into the Caspian.

There cannot, therefore, be a great difference in the level of these two basons; neither have they any outlet, though they receive great rivers. There is another great lake in the middle of Persia, called the Zara, which receives the river Hindenmend, of near 2 50 miles in length, besides other streams. There is another such in Asia Minor. The Sea of Sodom is another instance. And in the high countries before mentioned, there are many salt water lakes, which receive little rivers, and have no outlet.

The rivers of Africa are but little known; whether the establishinent of an European nation in Egypt will assist in developing the interior of that continent, remains to be proved. The Nile is, perhaps, better known to us than any river out of Europe. This celebrated stream, which from time immemorial has fertilized Egypt, is said to be 2820 miles, including all its windings, from its source to its mouth; and yet both in length and size it is inferior to several other rivers, both in the old and new worlds. The discovery of its sources was said to be often attempted both by the ancients and moderns; but Mr. Bruce su poses that they failed in their attempts, and that himself was the first European who visited its original springs, and accurately traced its course.

According to this gentleman the Nile rises in the country of the Agows, in a marshy valley, near the village of Geesh. This village is situated in the Mountains of the Moon, in the higher Ethiopia.

"About the middle of this marsh, and not quite forty yards from the foot of the Mountain of Geesh, rises a circular hillock, about three feet from the surface of the marsh itself, though founded, apparently, much deeper in it. The diameter of this hillock is not quite twelve feet, and it is surrounded by a shallow trench, which collects the water, and sends it off to the eastward. This is firmly built of sod, and kept constantly in repair by the Agows, who worship the river, and perform their religious ceremonies upon this as an altar. In the midst of it is a circular hole, in the formation or enlargement of which the work of art is evidently discernible. It is always kept clear of grass and aquatic plants, and the water in it is perfectly pure and limpid, but without any ébullition or motion discernible on its surface." The mouth is some parts of an inch less than three feet in diameter, and at the time Mr. Bruce first visited it (Nov. 5, 1770), the water stood about two inches from the brim; nor did it either increase or diminish during all the time of his residence at Geesh. On putting down the shaft of a lance, he found a very feeble resistance at six feet four inches depth, as if from week rushes and grass; and about six inches deeper, he found his lance had entered into soft earth, but met with no obstruction from stones or gravel; and the same was confirmed by using a heavy plummet, with a line, besmeared with soap. This is the first fountain of the Nile.

The second fountain is situated at about ten feet distant from the former, a little to the west of south; and is only eleven inches in diameter, and eight feet three inches deep.

The third is about twenty feet south, south-west, from the first, the mouth being somewhat more than two feet in diameter, and five feet eight inches in depth.