governed by one of his subjects, a native of Kashna, named Mohamed Mishnee.'-Id. p. 96. This is in direct contradiction to what is laid down by the sultan on the map which he caused to be drawn for Clapperton, of which a fac-simile is given in the Appendix. It is there made to flow easterly, at a point a little below Nyffe, and continues to do so as far as the meridian of Katagum, or to the end of the paper; and along the line of the river there is written in Arabic, This is the river (bahr) Kowara, which reaches Egypt, and which is called the Nile.' How then are we to reconcile these contradictions? Has Clapperton been led astray by the ambiguous meaning of the word bahr, which signifies equally a sea, a lake, and a river? That the sultan did not mean the ocean may, perhaps, be inferred from a note in another part of his map, which says, 'from this part of the country to the salt sea,' &c. Besides, neither in his map nor his memoir are there any such names as Fundah or Tagra, nor are any such known along the coast. It is true he calls Raka his port or harbour; but this means nothing more than that it is the last town in his dominions, lying on the Kowara, where the canoes from Timbuctoo discharge and receive cargoes, the word mára-kéb applying to all manner of floating craft. From hence to Yarba, which he states to be the great mart where slaves for the Christians assemble, kafilas go by land, and also from Yarba to a place called Atagara, near the sea-coast, of which it is said on the map-in it the talking bird is found; in it the Christians meet the people of Yarba for trade; in it the slaves are sold; and to it the wadáa, or cowrie-shell, is imported." The Sheikh Bahana, of Gadamis, told Major Laing that the river was checked in its southerly course, below Youri and Raka, by the intervention of a high chain of mountains, and that in the dry season it had scarcely any water in it at those places; which is, in fact, the true character of all intra-tropical streams, more especially in flat countries; but as the sheikh's knowledge of the river terminated at Raka, from whence he crossed the mountains, Major Laing has an hypothesis of his own, that it turns westerly, and discharges itself through the Volta;--the least likely, in our opinion, of all the conjectures which have as yet been hazarded. Major Denham seems to incline to the opinion that the Shary is the Kowara. There is a note in Clapperton's rough journal, made when on the Shary, purporting that the inhabitants of Showey all agree that the Shary comes from the south, and that its source is in the mountains, to the southward of Boussa; that at Boussa a branch is thrown off, which passes to the southward of Darfoor, Wadai, and Baghermie, and that it enters the Nile at Serenaar. เ Sennaar. We give little credit to this throwing off branches,' which rarely happens except on level tracts of swampy lands, or on the deltas of rivers; and a very intelligent man, of the name of Bellal, who had been at Boussa, told Major Denham that the Kowara did not give off a branch, but that a confluence of two branches took place at Boussa, the one from the south, the other from the north-west. The southerly branch no doubt exists, as the Shary was found to be in a state of flood in January and in June, which could not happen unless from the influence of rains to the southward of the line. Thus, with regard to the Kowara, the present mission has afforded us little information. We know, indeed, that the Shary and the Yeou pour their waters into the Tsad, but we know not yet whether the lake has an outlet to the eastward, or whether the water is carried off by evaporation. The information which Major Denham received from the Arabs would seem to favour the latter hypothesis. This is, to be sure, only Arab information, but the story is substantially the same that Burckhardt collected to the eastward, namely, that the Bahr-el-Ghazal, once a river flowing out of the lake, is now a dry valley, in consequence of the water of the lake having subsided. The high bank on the western side, which obviously once formed its shore, but is now in some places two or three miles from the water, would seem to countenance the story of the diminution of the lake; which may have. happened from a very natural cause, and not by a miracle, as the Arabs believe, in consequence of a holy man being murdered at the outlet through the Bahr-el-Ghazal, which from that moment ceased to flow-just as the Greek epigram makes the fountain to be dried up by a murderer washing his blood-stained hands in it, • Η παρος ενυδροισι λιβαζόμενη προχοαισι, Πτωχη νυν Νυμφών, μέχρι και εις σταγονα. If the fact be as stated, some new outlet, the result of the softer materials giving way, must have found a lower level than the old water-course, and robbed it of its stream; or, as another Arab story has it, the water may have forced its way under ground, and now rush out near Fittre. It would be idle to suppose that the climate has changed, the quantity carried off by evaporation decreased, or the rains diminished; or that the Yeou and the Shary have failed of their usual supply. The story, therefore, of there being no outlet is, we think, inadmissible, But having discussed this question in a former Number, and come to the conclusion, on physical principles, that a lake perfectly fresh, like that of the Tsad, must necessarily have an outlet, either above or below the surface, it will not be necessary to notice the frivolous objections of M. Jomard to a point so well established, established. We may just observe, however, that the example which he offers to the contrary, of the lake Segistan in Persia, does not apply, as it is well known that the water of the Hirmand river is merely dammed up by sand, through which, after forming a lake, it percolates, and does not pass off by evaporation : but as he boldly asserts that, from positive facts, and on scientific data,' the confluence of the waters of the Tsad with the Nile of Egypt is impossible, we feel ourselves called upon to show that it is not only possible, but probable. 6 6 6 He says that Debod, near Syène, 250 leagues from the mouth of the Nile, has been found by barometrical observation to be 543 feet above the Mediterranean, to which it has a fall of two feet per league; that as Debod is 325 leagues from the confluence of the Bahr-el-Abiad, the latter must be 1193 feet above the level of the sea. This deduction being neither from fact nor observation, but from an absurd theory of his, that rivers run on a logarithm,' or, as he now has it, by the Rule of Three,' will, we presume, not go for much; still less his assertion that the source of the Bahr-el-Abiad is, d'après les meilleures autorités,' about 350 leagues from its confluence with the Nile. The bes authorities! he knows there is not one authority, good or bad; we are only supposing the Tsad to be the source of this river, and we are ready to grant him his 350 leagues, which concession gives him, by his rule, an additional elevation of 700 feet, making the source of the Bahr-el-Abiad, or the lake, 1880 feet above the level of the Mediterranean. It is quite certain that if the Tsad be only 1200 feet above the sea, as Dr. Oudney makes it, and the confluence of the Bahr-el-Abiad with the Nile 1193 feet, as gratuitously assumed by M. Jomard, the waters of the former could never reach that point of confluence; but the fact is, we are utterly ignorant of the elevation of this point; and even that of the Tsad is but an approximation. We find it stated that, at Tripoli, the barometer was registered regularly three times a day for three months, the mean height during that period being 30. 39 inches; that about the middle of the desert it generally stood at 28. 50, and at Kouka from 28., 72 to 29 inches. Here we have some data to go upon. Taking, then, the mean of the two latter, we shall have 1340 for the approximate height of the lake, which is 140 more than Dr. Oudney has stated it to be. We are content, however, with taking the elevation at 1200; the direct distance from the lake to the confluence of the Abiad with the Nile at 1100; and from thence to the Mediterranean the same; we have then 2200 miles, with an elevation of the source equal to 1200 feet, which gives a fall of 64 inches per mile. Comparing this with that of the Amazons, which Condamine makes to be less than 7 with the Mississippi, which Schoolcraft's data make less than 6* -with the lower part of the Ganges, which Major Rennell makes less than 5—we need not hesitate to admit the fall of the Bahr-el-Abiad and the Nile to be amply sufficient to convey the waters of the Tsad into the Mediterranean. But to pass over the, at best uncertain, results of barometrical admeasurements, if it should be found that the country to the eastward is of the same kind as that to the westward of the lake, a fall of two or three inches per milet would be quite enough for a series of lakes and swamps to drain off the water; and the supposition that such is the fact is consistent with every information that has as yet been collected. The Bahr, now Wad, el-Ghazal, the very name of which implies the nature of the surface, and which, according to the accurate Burckhardt, is a wide extent of low ground, without any mountains,' is the first beyond the lake; then Fittre, in which by all account there is a great lake, or chain of lakes; beyond, in Dar Karka, there is said to be a great river, called Bahr-el-Freydh, or the inundating river, and beyond this a large fresh-water lake, called Wadey Hadaba; and then farther on is Dar Saley, of which Burckhardt says-In the rainy season, which usually lasts two months, large inundations are formed in many places, and large and rapid rivers then flow through the country. After the waters have subsided, deep lakes remain in various places, filled with water the whole year round, and sufficiently spacious to afford a place of retreat to the hippopotami and crocodiles which abound in the country.' Then we are informed by M. Jomard, that a French gentleman, of the name of Hey, has been up the Bahr-elAbiad 180 miles, and that it there maintained the character given to it by Bruce, of being a dead-flowing river.' Putting these notices together, and considering what the Yeou is to the westward of the lake, as far as Katagum, where not a pebble is to be found on the surface, which is one flat of lake, swamp, or sand, we think we need not boggle much as to the insufficiency of the fall for carrying the waters eastward of the Tsad. We must therefore adhere to the conclusion we came to in a former Article, viz. that the junction of the waters of this great lake with those of the Nile is not only possible, but extremely probable. Schoolcraft, by an extrao, inary blunder of making the dividend the divisor, gives a mean fall of two feet three ines to the Mississippi; and Jomard, who has written three pamphlets on the slopes of rivers, repeats the blunder.-See Q. Rev. No. LVII. The lower part of the Mississippi has no more fall than this. Major Long has calculated the head of the Illinois at 450. The length of this river to its junction with the Mississippi is 1200 miles, and of the latter from thence to the Gulf of Mexico 1200 more: the fall being 450 feet in 2400 miles, or 2 1-4 inches per mile-yet with this gentle slope its current is impelled with a velocity of more than three miles an hour.-Quar. Rev. No. LVII, ART. ART. XII.-A Letter to Sir Henry Halford, Bart. President of the College of Physicians, proposing a Method of Inoculating the Small-pox which deprives it of all its Danger, but preserves all its Power of preventing a second Attack. By R. Ferguson, M. D. Member of the College of Physicians of London and Edinburgh. 1825. ABOUT twenty years ago, when it was proposed to purify the medical profession from quackery and ignorance by legis lative enactments, the late Dr. Gregory of Edinburgh published a letter on the subject, in which he remarked that England is a free country, and the freedom which every free-born Englishman chiefly values, is the freedom of doing what is foolish and wrong, and going to the devil his own way. This is strikingly exemplified in the present state of vaccination in Great Britain, compared with its state in other countries of Europe. In the latter, general vaccination was ordered by government; no one who had had neither cow-pox nor small-pox could be confirmed, put to school, apprenticed, or married, Small-pox inoculation was prohibited; if it appeared in any house, that house was put under quarantine; and in one territory no person with small-pox was allowed to enter it. By such means the mortality from this disease in 1818 had been prodigiously lessened. In Copenhagen, it had been reduced from 5500 during 12 years to 158 during 16 years. In Prussia, it had been reduced from 40,000 annually to less than 3000; and in Berlin in 1819 only 25 persons died of this disease. In Bavaria only 5 persons died of small-pox in eleven years, and in the principality of Anspach it was completely exterminated. In England, on the other hand,-in England, the native country of this splendid and invaluable discovery, where every man acts on these subjects as he likes, crowds of the poor go unvaccinated; they are permitted not only to imbibe the small-pox themselves, but to go abroad and scatter the venom on those whom they meet. A few years ago it broke out in Norwich, and carried off more persons in one year, than had ever been destroyed in that city by any one disease, except the plague. A similar epidemic raged at Edinburgh; and last year it destroyed within one of 1300 persons in the London bills of mortality. Before the introduction of inoculation, the small-pox was the most loathsome and fatal disease with which Great Britain was afflicted. It killed about one out of four of those whom it attacked, and left many of the survivors with blinded eyes, scarred faces, and ruined constitutions. When, therefore, inoculation was introduced into this island, it seemed a prodigious improvement; by this simple contrivance, especially after the method |