wards noticed. Of this kind are the following obfervations, for which, however, the author did not require the waters of the Nile.

• Citizen Berthollet read a memoir on the formation of ammoniac; he explained the nature of the precipitate that results from the diffolution of tin, in confequence of the mixture of the muriatic with the nitric acid. This precipitate is not, as has been hitherto fuppofed, an indiffoluble oxyd of tin, but a combination of tin, highly oxydated with the ammoniac. The tin, between which and oxygene there is a great affinity, decompofes the nitric acid and the water, and then the azote and hydrogene unite together to produce the ammoniac. The laft fubftance combines with the oxyd of tin, and forms the precipitate we have just mentioned.

This explanation is fupported by the following experiments :the ammoniac is withdrawn from this precipitate by the action of heat and the admixture of lime. The diffolution of tin in the muriatic acid, even when impregnated with the oxygenated muriatic acid, does not then afford any precipitate; but this is formed the moment that a little ammoniac is poured in. The muriatic diffolution of tin, to which is added the oxygenated muriatic of potash, preferves it without being fubject to turn thick, even when it is expofed to heat.

It is highly important in the art of dyeing to be able to keep the diffolution of tin without its either getting foul, or the oxyd of tin fettling at the bottom, by means of precipitation. It has been propofed that it should be prepared with the muriatic acid alone, and that the dyer fhould impregnate it with the oxygenated muriatic acid during each operation; but, inftead of this embarraffing impregnation, which is attended with great uncertainty in respect to the proportions, citizen Berthollet propofes to add a determinate quantity of the oxygenated muriate of potash, by means of which, tin highly oxydated ceafes to folicit the decompofition of water, and confequently the formation of ammoniac; fo that the diffolution is thus preferved in an uniform ftate.' P. 6.

M. Beauchamp delivered a narrative of his voyage from Conftantinople to Trebifond, for the purpofe of afcertaining the longitude of the latter city, in order to obtain the precife length of the Black Sea. The difference of longitude between Paris and Trebifond is not, as Bonne fuppofed, 43°, but 37° 18′ 5′′ only, which fubtracts more than 80 leagues from its fuppofed length.

The-palm tree which produces the doùm is the cufiofera of Theophraftus. In the manufacture of Indigo the Egyptian artifts bruife the plant after having macerated it an hour in water, by which the vegetable mucilage mixes with the fæcula and injures its colour. The deftruction of the marble or granitic columns appears owing to the formation of muriatic

falts, which affects particularly the calcareous ftone; but the changes in the granite are more probably owing to the alternate moisture and drynefs, from the fucceffive influence of the dews and hot fun. The propofed objects of inquiry are highly judicious and proper. We trust that the fcientific affiftants have had time and leisure to carry at least some of these into execution.

Extract of a Report delivered to the Inftitute, relative to the Manufacture of the Saltpetre and Gunpowder of the Country. By M. Andreoffy.'

Egypt produces two of the ingredients of gunpowder in great perfection, charcoal prepared from the ftalks of the lupin, and nitre, found with its alkaline bafis in a foffil state. Sulphur only is imported. About 1400 weight of falt-petre is exported, and nearly as much gunpowder, the latter at the rate it was fold in France previous to the revolution. A defcription of a route from Cairo to Sfalehhyeh fills up (fomewhat heterogeneously). the remainder of this article. The country defcribed is from Cairo to Suez; and the view of this region, fo little known, deferves our particular attention.

This route, which is that followed by the caravans, in their journey to Syria, aftonishes the European on account of the fantaftical appearances it exhibits: it feems to form the boundary between Egypt and the defert. The fands are always on your right, the cultivated lands conftantly on your left; the human eye is bewildered in the extent of the first; it gladly repofes on the other. The more you advance, the more Egypt is covered with woods:" the villages are fcarcely diftinguishable amidst the enormous maffes of date trees. Large fycamores are not uncommon, and almost every where we meet with vaft inclofures of acacia and citron trees. But it is neceflary to prevent all illufion while, depicting these groves; neither verdure, nor flowers, nor rivulets, embellifh their neighbourhood: Trees, which are accompanied by fo many charms in Europe, here infert their roots in an 'argillaceous foil, yawning with fiffures, and every where evincing the aspect of the moft hideous poverty.

If the eye fhould wish to fix itfelf on one fide, on a more active vegetation, a little reflection deftroys the momentary impreffion, for the outline of the defert is at the fame time beheld making. an incurfion on the cultivated land. The hillocks deftitute of cupolas exhibit only abandoned habitations, and at every step we meet with the traces of agriculture, nearly effaced by the fand, while we fearch in vain for a small portion of the arid border that has been reflored to husbandry.

From the village of El-mardje may be diftinguished the spot called El khanqah, which is confidered as one of the most im portant places in the country. Between thefe two villages is a CRIT. REV. VOL. XXX. September, 1800.

D

tufted grove; it occupies the fummit of an afcent, that inclines gently towards the defert, and terminates at the famous lake Berketel-hhadje (the lake of pilgrims). At prefent it is nothing more than a parched mass, surrounded by feveral rows of trees.

The hamlet which I have just described, appears to correfpond with that which formerly contained the Pelufiac branch; this was the most easterly channel of the Nile; it advanced towards the defert, and has probably difappeared in confequence of the overwhelming whirlwinds. The water formerly conveyed by it is no longer vifible, while, at a fhort diftance in its rear, canals ftill exift in the place of those which flowed towards the mouth of the Mendezian channel.' P. 48.

Belbeys, in this tract, the ancient Bubaflum, was once the bulwark of Egypt against Syria, an honour fince transferred to El-Arifh; but the journey in the latter part is not peculiarly interesting. Trees are planted in groups; and thefe infulated woods are called, by the Arabs, ifles. The inhabitants are chiefly Bedouins, and the peafant feems to enjoy more independence and fecurity than the inhabitants of Čairo and other towns they feem beyond the reach of the tyranny of the Mamlukes, as they are at a diftance from canals, the only mode of conveying their plunder.

Circular Letter, from M. Defgenettes, to the medical Men of the Army of the Eaft, relative to a Plan for drawing up a Phyfico-Medical Topography of Egypt.'

M. Defgenettes gives very falutary advice to the medical practitioners attending the army, of which we find they have availed themfelves. The plan is addreffed to them, and would be of little fervice were we to detail it.

Report relative to Pompey's Column. By M. Norry.' The French philofophers raised themselves to the top of this column, following the method firft employed by an English failor, though executed in a lefs intrepid manner.

• It is fituated on a gentle eminence, and placed on a base, which the barbarians have undermined; a centre of one metre and twenty-eight centimetres (four feet fix inches), in form of a square, ferves as its fole fupport. This centre is formed of the fragment of an Egyptian monument, which appears to be of a filicious nature, and must have been brought to this place, as the hieroglyphic characters are reverfed. On an attentive examination of the wafte. committed beneath the pedestal, it is perceived that the rubbish, being laid in heaps, has occafioned the column to lean twenty-one centimetres (eight inches); and it is undoubtedly to this caufe that may be attributed a deep crevice of about four metres eighty-feven centimetres (fifteen feet) in length, at the lower part of the shaft.' P. 71.

The pedestal is ten feet in height; the bafe (we fuppofe each fide of the bafe is meant) five feet 6.3 inches; the fhaft fixty

three feet 1.3 inches; the capital nine feet 10.6 inches; the diameter of the column diminishing from eight feet four inches to seven feet 2.8 inches near the aftragal. The total height eighty-eight feet fix inches. The pillar is of Theban granite. The capital is of the Corinthian order, but the proportions of the fhaft approach rather the Iönic. The capital and the pedestal seem therefore to be comparatively modern, and the column, on fome occafión, to have been re-erected.

A Memoir relative to an Optical Phænomenon, known by the name of Mirage. By M. Gafpard Monge.'

The mirage, by failors, is ufually called a fog-bank, giving, in a mifty atmosphere, the appearance of a bank or land. The prefent phænomenon is very different, confifting of the appearance of water furrounding objects on a diftant horizon, when the fun has acquired a confiderable altitude, and the intervening country is plain and hot. From this water the objects are indiftinctly reflected. M. Mohge gives a very laboured folution of the mirage on optical principles, which we cannot abridge, and which we fufpect to be erroneous. For the folution, it requires only that the fubjacent ftratum fhould have different refractive powers from the atmosphere in general, fuffering the rays, which fall on it in an angle, when they are commonly refracted, to be reflected. Without fome alteration in this fubjacent ftratum of air, no optical explanations will fucceed. A fecond image of an object inverted, placed vertically over the firft, has been often noticed and explained; and the double rainbow, forming, by the reflected image of the fun from water, two other bows, is not without an example. The explanation is not difficult.

Obfervations on the Wing of the Oftrich. By M. Geoffroy." As the oftrich connects the quadruped with the bird, its œconomy becomes of importance, and, in the peculiar organs which form this connexion, has not been properly explained. In the ftructure of its wing, the muscles have not the bulk or length of those of birds, nor have they the fame advantageous attachment by means of the brisket, or a proportionally extended fternum. The air veffels are reduced both in number and extent, and the merry-thought, though it exifts, is rendered ufelefs by a divifion at the centre. The ftructure of the feathers is well known not to be adapted for flight.

Although ufelefs in the prefent cafe, thofe rudiments of the merry-thought have not been suppressed, because nature never proceeds by rapid ftrides, and always leaves the veftiges of an organ, even when it is fuperfluous, provided this organ has acted an important part in the other fpecies of the fame family, Thus the veftiges of the wing of the caffiowary are to be found beneath the fkin that covers the fides; thus, alfo, at the internal angle of the

human eye, there is a fwelling of the fkin which we recognise as the rudiments of the nitant membrane, with which many quadrupeds and birds are provided.' P. 97.

Obfervations on the Arabian Horfes of the Defert.'

We do not perceive, in thefe remarks, any valuable addition to our knowledge of this fubject, fupplied by various travellers of the Eaft; at leaft to knowledge on the accuracy of which we can depend, or what we could, with propriety, enlarge on. Account of the prevailing Ophthalmia of Egypt, by M. Bruant.'

This article is written in confequence of the recom mendation, and from the plan, of M. Defgenettes. Befides the endemic ophthalmia, from fand, duft, or acrid vapours, which is violent and painful, often terminating in ulcers on the cornea and lofs of fight, there is another kind arifing from bilious acrimony in the ftomach and bowels; and a third, chiefly fpafmodic, more ftrictly perhaps from irritability. There is nothing peculiarly new or valuable in the methods. recommended for treating it.

Extract of a Letter from Adjutant-General Julien.'

Relates to a form of making oaths in Egypt, and the author obferves, that many Egyptian cuftoms illuftrate circumstances in facred hiftory, which have been confidered as fupernatural, because only extravagant.'

Defcription of a new Species of Nymphæa. By M. Savigny.'

The beauty of the white water lily, the nymphæa lotus, has attracted the attention of naturalifts and obfervers, and the blue has probably been confidered as a variety only. Out author confiders it as a diftinct fpecies, differing fpecifically from the nymphaea lotus in its leaves and anthers. The former is characterifed foliis dentatis; the latter, foliis repandis; the nymphæa lotus, antheris apice fimplicibus;' the nymphæa coerulea antheris apice fubulato-petaloideis.'

Remarks on the Topography of Menouf in the Delta. By M. Carrie.'.

This is another part of M. Defgenettes' plan; but fuch minute circumstances cannot be abridged, and offer nothing interefting to the general reader.

An Arabian Ode on the Conqueft of Egypt. Tranflated from the Original. By M. J. J. Marcel.'

The following general remarks on Arabian poetry merit our attention.

Arabian literature was in its earlier age fimple and divefted of ornament;, the language partook of the rude manners of the favage ftate, and the people among whom it originated; but at the fame time, in proportion as the Arabs were in a ftate more approaching