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wards noticed. Of this kind are the following observations, 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 dissolution of tin, in consequence of the mixture of the muriatic with the nitric acid. This precipitate is not, as has been hitherto fupposed, an indissoluble oxyd of tin, but a combination of tin, highly oxydated with the ammoniac. The tin, between which and oxygene there is a great affinity, decomposes the nitric acid and the water, and then the azote and hydrogene unite together to produce the ammoniac. The last substance combines with the oxyd of tin, and forms the precipitate we have just mentioned.

• This explanation is supported by the following experiments :the ammoniac is withdrawn from this precipitate by the action of heat and the admixture of lime. The dissolution 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 disso. lution of tin, to which is added the oxygenated muriatic of potash, preserves it without being subject to turn thick, even when it is exposed to heat.

. It is highly important in the art of dyeing to be able to keep the dissolution of tin without its either getting foul, or the oxyd of tin settling at the bottom, by means of precipitation. It has been proposed that it Mould be prepared with the muriatic acid alone, and that the dyer should impregnate it with the oxygenated muriatic acid during each operation; but, instead of this embarrassing inpregnation, which is attended with great uncertainty in respect to the proportions, citizen Berthollet proposes to add a determinate quantity of the oxygenated muriate of potash, by means of which, tin highly oxydated ceases to solicit the decomposition of water, and consequently the formation of ammoniac; so that the diffolution is thus preserved in an uniform state.' P.6. · M. Beauchamp delivered a narrative of his voyage from Constantinople to Trebisond, for the purpose of ascertaining the longitude of the latter city, in order to obtain the precise length of the Black Sea. The difference of longitude between Paris and Trebisond is not, as Bonne supposed, 43°, but 37° 18' 5" only, which subtracts more than 80 leagues from its supposed length. ' The-palm tree which produces the doùm is the cusiofera

of Theophrastus. In the manufacture of Indigo the Egyptian artists bruise the plant after having macerated it an hour in water, by which the vegetable mucilage mixes with the fæcula and injures its colour. The destruction of the marble or granitic columns appears owing to the formation of muriatic

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falts, which affects particularly the calcareous fone; but the changes in the granite are more probably owing to the altera nate moisture and dryness, from the successive influence of the dews and hot sun. The proposed objects of inquiry are highly judicious and proper. We trust that the scientific affistants have had time and leisure to carry at least fome of these into execution.

Extract of a Report delivered to the Institute, relative to the Manufacture of the Salopetre and Gunpowder of the Country. By M. Andreoffy.' · Egypt produces two of the ingredients of gunpowder in great perfection, charcoal prepared from the stalks of the lupin, and nicre, found with its alkaline baas in a foffil ítare. Sulphur only is iinported. About 1400 weight of salt-petre is exported, and nearly as much gunpowder, the latter at the rate it was fold in France previous to the revolution. A description of a route froin Cairo to Slalehhyeh fills up (somewhat heterogeneously). the remainder of this article. The country described is from Cairo to Suez; and the view of this region, so little known, deserves our particular attention, T.,::.

"This route, which is that followed by the caravans, in their journey to Syria, astonishes the European on account of the far-' taftical appearances it exhibits: it feems to forin the boundary between Egypt and the desert. The lands 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 repoles on the other. The more you advance, the more Egypt is covered with woods : the viHages are fcarcely distinguishable anvidst the enormous males of date trees. Large sycamores are not uncommon, and almost every where we meet with vart inclosures of acacia and citron trees. But it is necessary to prevent all illufion while depicting these groves; neither verdure, nor flowers, nor rivulets, embellish their neighbourhood: Trees, which are accompanied by so many charms in Europe, here insert their roots in an 'argillaceous foil, yawning with fiflures, and every where evincing the aspect of the most hideous poverty...

"If the eye should with to fix itself on one side, op a more active vegetation, a little reflection deftroys the inomentary impresa fion, for the outline of the desert is at the same 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 land, while we search in vain for a small portion of the arid border that has been restored to husbandry.

« From the village of El-mardje may be diftinguished the spot called El khanqah, which is considered as one of the most important places in the country. Between these two villages is a

CRIT. REV. VOL. XXX. September, 1800. D

tufted grove; it accupies the summit of an ascent, that inclines gently towards the desert, and terminates at the famous lake Berketa cl-hhadje (the lake of pilgrims). At present it is nothing more than a parched mass, surrounded by several rows of trees.

• The hamlet which I have just described, appears to correspond with that which formerly contained the Pelusiac branch; this was the most easterly channel of the Nile; it advanced towards the desert, and has probably disappeared in consequence of the overwhelming whirlwinds. The water formerly conveyed by it is no longer visible, while, at a thort distance in its rear, canals still exist in the place of those which flowed towards the mouth of the Mendezian channel.' P.48.

Belbeys, in this tract, the ancient Bubaslum, was once the bulwark of Egypt against Syria, an honour since transferred to El-Arish ; but the journey in the latter part is not peculiarly interesting. Trees are planted in groups; and these insulated woods are called, by the Arabs, ines. The inhabitants are chiefly Bedouins, and the peasant seems to enjoy more independence and security than the inhabitants of Cairo and other towns: they seem beyond the reach of the tyranny of the Mamlukes, as they are at a distance from canals, the only mode of conveying their plunder.

• Circular Letter, from M. Desgenettes, to the medical Men of the Army of the East, relative to a Plan for drawing up a Physico-Medical Topography of Egypt.'

M. Desgenettes gives very falutary advice to the medical practitioners attending the army, of which we find they have ayailed themselves. The plan is addressed to them, and would be of little service were we to detail it.

! Report relative to Pompey's Column. By M. Norry.

The French philosophers raised themselves to the top of this column, following the method first employed by an Englilla sailor, though executed in a less intrepid manner.

• It is situated 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, serves as its sole support. 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 reversed. On an attentive examination of the waste. committed beneath the pedestal, it is perceived that the rubbish, being laid in heaps, has occasioned the column to lean twenty-one centimetres (eight inches); and it is undoubtedly to this cause that may be attributed a deep crevice of about four metres eighty-seven centimetres (fifteen feet) in length, at the lower part of the haft.' P. 71.

· The pedestal is ten feet in height; the base (we suppose each side of the base is meant) five feet 6.3 inches; the shaft 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 astragal. 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 shaft approach rather the Tönic. The capital and the pedestal seem therefore to be comparatively modern, and the column, on some occasion, to have been re-erected.

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

The mirage, by sailors, is usually called a fog-bank, giving, in a misty atmosphere, the appearance of a bank or land. The present phænomenon is very different, consisting of the appearance of water surrounding objects on a distant horizon, when the sun has acquired a considerable altitude, and the intervening country is plain and hot. From this water the objects are indistinctly reflected. M. Monge gives a very laboured solution of the mirage on optical principles, which we cannot abridge, and which we suspect to be erroneous. For the lo. lution, it requires only that the subjacent stratum Thould have different refractive powers from the atmosphere in general, suffering the rays, which fall on it in an angle, when they are commonly refracted, to be reflected. Without some alteration in this fubjacent stratum of air, no optical explanations will succeed. A second image of an object inverted, placed verti. cally over the first, has been often noticed and explained; and the double rainbow, forming, by the reflected image of the sun from water, two other bows, is not without an example. The explanation is not difficult.

i Observations on the Wing of the Ostrich. By M. Geoffroy.'

As the ostrich connects the quadruped with the bird, its æconomy becomes of importance, and, in the peculiar organs which form this connexion, has not been properly explained. In the structure of its wing, the muscles have not the bulk or length of those of birds, nor have they the same advantageous attachment by means of the brisket, or a proportionally extended sternum. The air vessels are reduced both in number and extent, and the merry-thought, though it exists, is rendered useless by a division at the centre. The structure of the feathers is well known not to be adapted for flight.

Although useless in the present cafe, those rudiments of the merry-thought have not been suppressed, because nature never proceeds by rapid strides, and always leaves the vestiges of an organ, even when it is fuperfluous, provided this organ has acted an important part in the other species of the same family, Thus the vestiges of the wing of the cassiowary are to be found beneath the skin that covers the Gides; thus, also, at the internal angle of the huinan eve, there is a swelling of the skin which we recognise as the rudiments of the nictant membrane, with which many quadrupeds and birds are provided.' P.97.

• Observations on the Arabian Horses of the Desert.' . We do not perceive, in these remarks, any valuable addition to our knowledge of this subject, supplied by various travellers of the East; at least to knowledge on the accuracy of which we can depend, or what we could, with proprietv, enlarge on.

• Account of the prevailing Ophthalmia of Egypt, by M. Bruant.'

This article is written in consequence of the recom, mendation, and from the plan, of M. Defgenettes. Besides the endemic ophthalmia, from sand, duit, or acrid vapours, which is violent and painful, often terminating in ulcers on the cornea and loss of light, there is another kind arising froin bilious acrimony in the stomach and bowels; and a third, chicfly spasmodic, more strictly perhaps from irritability. There is nothing peculiarly new or valuable in the methods recommended for creating it.,

• Extract of a Letter from Adjutant-General Julien.'

Relates to a form of making oaths in Egypt, and the author observes, that many Egyptian custoins illustrate circumstances in sacred history, which have been confidered as fupernatural, because only extravagant.'

• Description of a new Species of Nymphæa. By M. Savigny.'

The beauty of the white water lily, the nymp!ıæa lotus, has attracted the attention of naturalists and observers, and the blue has probably been considered as a variety only. Out author considers it as a diftinct species, differing specifically from the nyinphæa lotus in its leaves and anthers. The former is characterised « foliis dentatis ;' the latter, foliis repandis ;' the uymphæa lotus, antheris apice fimplicibus;' the nymphæa cærulea antheris apice subulato-petaloideis.'

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

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

• An Arabian Ode on the Conquest of Egypt. Translated from the Original. By M. J. J. Marcel.' • The following general reinarks on Arabian poetry merit our attention.

i Arabian literature was in its earlier age simple and divested of ornament;, the language partook of the rude manners of the savage state, and the people among whom it originated; but at the same time, in proportion as the Arabs were in a state more approaching

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