fource; which is faying in other words, that it fprings from a different region from that which gives rife to the Abyffinian branch; whence by his account, the fource of the White river should be very remote from that of the Blue river, in Abyffinia. But what fays his map? There, the limits of the periodical rainy feasons lie between fixteen degrees of latitude; and thofe of the perpetual rains, between 4 degrees; on each side of the equator. There alfo, the fource of the White river is placed in Ɛo north, and that of the Blue river in 11° only, with a difference of meridians of no more than 24° and one of the fprings of the latter is even near the 8th degree. Do these differences then conftitute different regions? We may add, that the White river is drawn on his map, much smaller than the eastern branch; which differs, as we have feen, totally from the description!

The fact we should conceive clearly to be, that the White river has a much more diftant fource than the other. Some light is thrown on this particular, by Maillet's faying that the White river runs nearly parallel to, and at the distance of 12, 15, and 20 journies from the Nile; which can only be true of two rivers that spring at a great distance from each other. We are of opinion, therefore, that Mr. Bruce, who faw the White river, has admitted its fuperior bulk, and ftate of fulness, at all feasons; properties which the other branch does not poffefs: (as to its being in the fame ftate, all the year, that we cannot fuppofe of any tropical river;) and hence, as he appears not to have made out his fyftem of a constant rainy feafon, to fupply the river in question, the reader will probably be inclined with us, to fuppofe, that a stream, at all times confeffedly larger than another, has, in all probability, a more remote fource.' P. 436.

The major might have added, as we have remarked on a former occafion, that the ancients totally diftinguish the Abyffinian river from the Nile, as they term the former the Aftapus, a name feemingly connected with the Aftraboras, another river, which flowed by Meroë. He concludes (p. 441), "that the diftant fource of this celebrated river is certainly not in Abyffinia, but in fome country to the westward of it." He would here certainly have added the irrefragable teftimony of Mr. Browne; but it appears, from p. 480, that Mr. Browne's work only appeared when the feventeenth fection was in the press.

'Since this fection went to the prefs, the author has had the fatisfaction to peruse Mr. Browne's Travels in Africa; which, he conceives, will be claffed amongst the first performances of the kind. The aids it brings to geography are great, and will probably lead to further discoveries; as it forms a link between Abyffinia on the east, and Bornou on the weft. Moreover, it confirms, in a great degree, two pofitions advanced in the prefent fyftem of African

geography: firft, that the Niger does not join the Nile: and, fecondly, that the most remote head of the Nile is not fituated in the quarter of Abyffinia, but far to the fouth-west of it.' P. 480.

The following obfervations concerning the alluvions of rivers prefent one among many inftances of the major's happy application of recent knowledge to ancient circumftances.

'No doubt, when we carry back our ideas to the time when the fea washed the base of the rock, on which the pyramids of Memphis ftand, the present base of which is washed by the inundation of the Nile, at an elevation, moft probably, of 70 or 80 feet, above the furface of the fame fea; we are loft in the contemplation of the vaft interval of time, that muft neceffarily have elapfed fince the foundation of the Delta was firft laid. But, appearances fpeak too clear a language to be misunderstood: and we are borne out in the fuppofition that the Delta has been formed piece-meal, by a process which we fhall now endeavour to defcribe. The following may accordingly be taken, as a specimen of the progress of alluvion; and which may be feen, in all the different stages of the process, at the mouth of any large river, that depofits rapidly, and plentifully.

All rivers preferve, to a certain extent of space, which is proportioned to the velocity of their streams, a current of water, intò the fea, beyond the points of land, that form their embouchures; when, by the continued resistance of the sea, they at last lose their motion. The mud and fand fufpended in thefe waters, during their motion, are depofited, when that motion ceases; or rather, they are gradually depofited, as the current flackens: according to the gra vity of the fubftances that are fufpended. This depofition, then, will form a bank or fhallow, in the fea; and which will be of a fan-like fhape, confiftently with the form, in which the water of the river difperfes itself. This bank is of very confiderable breadth; and is, of courfe, conftantly on the increafe, in height, as well as extenfion and the additions conftantly made to its breadth, will be on the fide towards the fea. Until the bank rifes up nearly to the furface, the river water which is continually poured into the fea, efcapes freely over it: but when the bank has rifen fo high, as to inclose the water in a kind of lake, it is then compelled to force its way through the bank: although the paffage will be both narrow and shallow, whilft the bank remains under water. This paffage is technically named a bar: for fuch it is, in refpect of the channel of the river, although it be the deepest part of the entrance to it.

The pofition of this opening through the bank, will be regulated by the direction of the stream of the river, at its termination in the fea; and this direction, again, by the prevalent motion of the fea, along the coaft; the mouth of the river always falling obliquely into the line of the fea current. Accordingly, when the river enters the fea obliquely, the bar will be at one fide of the bank;

and on that fide which is the fartheft down, in respect of the sea current. But if the river enter the fea, in a line perpendicular to its fhore, the opening, or bar, will be through the middle of the

bank.

As the bank rifes to the furface, the opening increases in depth and width, until it becomes abfolutely a continuation of the course of the river; fince its waters require the fame breadth and depth to efcape here, as in the upper parts of its courfe. And thus the upper part of the bank becomes gradually a portion of the firm land; whilft the outer part goes on accumulating, and the bar is gradually removed farther out: in effect, there will be a repetition of the fame order of things. And hence it will clearly appear, that the bank thus laid in the fea, by the current of the river, is, in reality, the germ of the growing alluvion.

• The bars are usually swept away every feason, by the periodical flood; which, although it cannot rife to a higher level than the fea, is increased in velocity, by the increase of the body of water, above: and alfo by that of its defcent; as the flood-fwells to a greater height above, and therefore forms a flope towards the fea. These floods also bring the greatest addition to the growing alluvion: and, not unfrequently, change the direction of the channel, and with it, of courfe, the pofition of the bar: their depofitions being laid farther out in the fea, by reason of the greater velocity of the current.

Having endeavoured to explain the mode in which the alluvion gains on the fea, we fhall next endeavour to explain the manner in which the changes and modifications of the exifting alluvions are wrought.

The alluvions thus formed in the fea, are, in their original ftate, flat, and are alfo on a level with the ordinary surface of the fea but as the furge repels that part of the deposited matter, which rifes to the furface, it will be raised somewhat above the level: and as this agency has regularly operated on all the new-made alluvion, it must have formed one continued level, but for the interpofition of the periodical floods, which have formed it into a regular flope, correfponding with its own.

As the alluvion, then, is extended into the fea, fo is its level gradually raised into a flope: an operation that is constantly going forward, but which cannot keep pace with the extenfion, because every addition to it occafions a deficiency in the flope.

Until the new formed alluvion was confiderably raised, it must have partaken very much of the character given it by Herodotus; who fays, that in ancient times, "the whole of Egypt, except the province of Thebes, was one extended marsh:" Euterpe, 4: and that when "the Nile rofe to the height of 8 cubits, all the lands above Memphis were overflowed." (Eut. 13.) Both of these traditions clearly point to a state of things that had exifted; although, probably, at a period too remote to be fixed; for there must have been a time when the Delta was not only a marsh, but was even co❤

vered with water; and when the fea must have advanced so near to the fite of Memphis, as to allow the annual flood to rife no higher than 8 cubits, or 12 to 14 feet, at that place. He afterwards remarks that it rofe 15 or 16 cubits in his time; which was the natural progrefs of things: as the point of contact of the land waters, with those of the fea, was removed farther out.

So long as the alluvion of the Delta remained in the state of a marth, the waters of the Nile, through the want of declivity to carry them off, and the preffure of the fea water from without, when the river was low, may be supposed to have formed a tissue of canals, interfperfed with lakes and marthes. But when the land began to acquire fome degree of folidity in the upper parts of the Delta, canals, in the nature of drains, would be formed by the hands of men, and dykes raised along the banks of rivers, in order to exclude the redundant waters from the appropriated lands. And this is probably the period referred to by Herodotus, when he defcribes the vaft and numerous canals by which Egypt is interfected;" and which he attributes to Sefoftris. Euterpe, 108. He was alfo told, that the fame prince made a regular distribution of the lands of Egypt, affigning to each Egyptian a fquare piece of ground; and that his revenues were drawn from the rent, which every individual annually paid him,

• As the land rose by depofitions, the waters would naturally confine themselves to fewer channels; fince the land, when in a firmer ftate, would require a greater force to divide it. At a time when the upper part of the Delta had acquired a degree of firmness and elevation, we learn from our author, that three natural channels, alone, conveyed the waters of the Nile to the neighbourhood of the fea; a quarter in which the alluvial land must ever be regarded as in an imperfect state of formation. At prefent, two alone convey it to the fame quarter, during the feafon when the river is not fwoln; and one of these is growing fhallow. Can it be doubted, then, that a delta is (comparatively speaking) land in an imperfect state of formation; that the natural progress toward completion is that of the river's confining itself to fewer channels; and that the inundation, from being a complete mafs of water, spread uniformly over the country, becomes merely an overflowing of the river, extending to a certain distance, and forming the country adjacent to each bank, into a flope of feveral miles in breadth, of which the highest part is the creft of the bank itfelf; from the circumftance of its depofiting more fediment near the bank, than at a distance from it? But as long as the alluvion continued too flat to communicate a sufficient velocity to the river, when in its low ftate, it would continue to separate itself into many different streams, although one of them would probably furpafs all the reft in bulk. On the above principle, then, as the greater flope, defcribed in page 485, extends itself downwards, the Delta ought to retire from it: or, in other words, the river, in its courfe through the high level, fhould flow unique;

and the bafe of the Delta fhould gradually contract: and this, we truft, will be fatisfactorily proved in the fequel.' P. 488.

Obfervations of fimilar curiofity and importance alfo occur with regard to the currents in the fea on the African coafts, which the major has the high merit of firft applying to the illuftration of general geography. The fection relative to the Oafes is replete with information; but we were furprised to find the major (p. 563), in oppofition to his own map of Africa, affuming the pofition, which we had before afferted, that Santaria is the fame with Siwa. We with that he would imitate our candour, and, when he points out our mistakes, at the fame time give us credit for our discoveries.

We were yet more furprised (in the twenty-firft fection) to find that the major was employing a whole army of engineers, and a battery of mathematical calculations, to establish this very point, which had long ago impreffed us, from comparing. modern travels with the Arabic geographers. He has however the merit of demonftrating that the temple of Jupiter Ammon was really discovered by Mr. Browne; a circumstance fince confirmed by Mr. Horneman, who, we fincerely hope, will be preferved from numerous dangers, and return with ample information concerning the interior of Africa. At the fame time, we must exprefs our with that the major would in future abandon a tone of decifion when treating of fo doubtful a fcience as the geography of diftant regions; for he will frequently find that the erection of mathematical principles upon fandy foundations is a moft dangerous abuse. We particularly allude to his calculations upon diurnal journeys, in themselves uncertain, as has been lamentably proved in the recent difcovery of the latitude of Mourzouk, which differs no less than two degrees, or near one hundred and forty miles, from the major's mathematical demonstrations. Such mifapplications of mathematical procedure are the more perilous, as they may difguife the groffeft error under the mask of the most authentic truth. Sufpenfe is always unpleasant to the human mind, and a young writer may be pardoned for being a stranger to the learned ignorance recommended by Mr. Gibbon; but even the formal engraving of a map gives it an aspect of reality; and it is far more fafe totally to omit what is uncertain, than, by giving ideal rivers and pofitions, to mislead the traveller, and perhaps induce him to propagate unintentional error. If we fuppofe, for inftance, that a river is laid down in any imaginary direction, a traveller may be induced to lose his time, and perhaps his life, in fearch of a non-existence; while, perhaps, if he had only trufted to his own spirit of inquiry, he might have made a real and import ant discovery,