While the ministers of the Emperor Francis II. were occupied in schemes for rendering the passes of the Tyrol more formidable to an invading enemy, the Government of France was employed in examining the different places at which it was most accessible, and in considering the mode of overcoming the difficulties which it would oppose to an army. The recollections before us are intended as supplemental to the Memoirs which have formerly been composed on this subject; the author having examined its openings on every side, and minutely laid down the nature of every country which joins to the Tyrol, on the South and on the North, on the East and on the West. The state of the principal roads, the hours of march between the chief places, the natural and artificial obstacles, the chains and branches of the mountains, the course of the rivers, and the resourses which in a military view the country is capable of affording, are the subjects of detail: but it would be uninteresting minutely to follow the writer through his various researches, and tiresome to enumerate the numerous vallies, gorges, &c. which are here specified. We shall content ourselves with adding, as a specimen of this work, the account of the lake Garda, which borders on the Tyrol, and which is not so generally known as some other lakes in this region of the Continent.

The lake Garda is about fifteen leagues long, and its mean breadth about three leagues. It is so much narrowed towards the upper part as to be scarcely 4000 metres or a league over; towards the middle, its width is double; and at the bottom it is four leagues wide. The head of the lake is shut in between Monte Baldo and the mountains of Bressan, which are cut perpendicularly from Gargano to Riva. The lower part is included between hills, to which learned Italians give the name of Colli-Benacesi. It receives the Sarca on the north; towards the west, the torrents of Ponal, Brasa, Lampion, and Toscolano; and on the east, the waters which run from Monte Baldo. The surface of the lake is broken by three islands, the Trimelone, Olivi, and Frati, and by the peninsula of Sermione, which projects from the middle of the lower side of the basin.

Its waters being extremely limpid, we perceive at a great depth the stones at the bottom, and the plants which cover them: but its depth is so very unequal that its mean cannot be easily assigned. At a small distance from the banks, it measures almost every where many metres: but the deepest parts are towards the north. The Count Bettoni, cited by the Abbé Volta, according to soundings exactly taken, found 79, 124, 161, and in short 584 metres of water between Castelletto and Gargnano: but Carli, in his history of Verona, says that the same admeasurement taken by M. Cocoli, mathematician of Brescia, gave him only 179" below Madona de MonteCastello, and sixteen metres of the escarpment in the deepest place

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of the lake; while on approaching the middle of the lake, he found but 129.

The water is very light, but it has rather a fishey taste. M. Zeviani says that it is very good to drink, boils easily, does not curdle soap, and boils vegetables perfectly well At the commencement of the summer, the water rises, which the fishermen attribute to the plants that spring up from the bottom of the lake: but which it is more natural to assign to the melting of the snows, and the heavy rains which fall at that season. The navigation is then often dangerous. When the water sinks, marshes appear in certain places; the exhalations from which, by the action of the sun, render the air unhealthy.

South and north winds prevail in the morning and in the evening, but the various directions of the gorges and vallies, which border on the lake, occasion currents of air, to which the inhabitants give names referring either to their effects or to the part of the shore from which they proceed. The Vexentina blows after changes of the weather, or when it becomes settled. The Toscano blows when the weather is about to change, and is often followed by a high wind. The names of these two refer to their direction; they are stormy, as is also that which blows from Garda, and is called Spizzocher, being often as tremendous as that from the north, but it is of short duration. The Andro, which blows from the side of Lonato, is little dangerous. Those of Ponal and Navenne, named from the places whence they proceed, are much to be feared in the summer season, taking the barks by surprize which sail in these directions: but these winds are not of long continuance. The Ora blows all the year, especially in April (Germinal) but it never disturbs the lake. The Sovero is the most furious, often violently agitating the whole mass of water; at which time, the lake presents the frightful appearance of a stormy sea. The vessels, which are overtaken by it, do not endeavour to resist it, and only think of shelter. These tempests commonly happen either in winter, when the snow is on the mountains; or in summer, when they become tremendous storms, which continue for two or three days. The appearance of the heavens indicates their approach.

The commerce of the lake is considerable, and it would become more so if the Mincio were rendered navigable. At Torri, Garda, Limon, Torbole, Peschiera, and Riva, the fishery is a very import ant object. The principal entrepôt or market is at Dezenzano: but there is another also at Torri. The people carry their fish to Venice, Milan, and even to Genoa; and every where it is much in request.

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On the eastern bank, the ports most frequented are those of Lafise, San Virgilio, and Malsonina: they are moreover the largest and most commodious. That of Torri is choaked up with sand, or at least subject to that inconvenience. Those of Bardolino and Brenzone are used only as ferries. That of Riva is the largest and the safest, and it is the entrepôt of the commerce of the Tyrol. Planks, framed timber, charcoal, &c. are sent from this point. Three fairs

Sardines, eels, trout, and carp are the fish which most abound. It is singular that in one part river fish are found, and in another those fish which belong to the sea.

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are

are held in every year; and the merchandise of the fair of Botzen passes by Torbole and Salo, or by Dezenzano, into Bressan and the Milanese. The largest barks carry 600 myriagrammes, from which their size diminishes almost to that of a fisherman's boat, able to carry only 125 myriagrammes, or 14 persons, with two or three watermen. When there is no wind, all the barks are rowed or towed along the shores: but they have a large square sail, and the largest have a rudder; the others are directed by an oar: none of them are decked. They never sail against the wind; and if, when they set out on a voyage, it blows rather briskly, they tack about. With a favourable wind, the largest barks make the most way, sailing nearly six miles in an hour; and a fishing boat, with four oars, can go four or five, if the wind be not contrary.'

This memorial terminates with an article on the Voralberg, (comprehending the segniories of Bregentz, Feldkirch, Pludenta, and Hohen-Embs) copied from l'Almanach du Tyrol for the year 1805, which is a publication of more extent, and includes more general and appropriate information, than most works of this kind. It contains various historical extracts, statistical memoirs, pieces of poetry, and anecdotes of bravery and patriotism. It is, in short, particularly calculated to excite the enthusiasm, energy, and attachment of the Tyrolese to the House of Austria.

Subjoined to the survey of the Tyrol, is a second Extract from a military survey of the Black Forest; being a continuation of details published in a preceding number, and signed Guilleminot, formerly chef de bataillon to the Etat Major of the army. As, however, we have not seen the former part, we shall not plunge headlong into the recesses of this formidable forest.

ART. VI. Dictionnaire des Sciences Naturelles, &c. i. e. A Dictionary of the Natural Sciences, &c. Tome III* 8vo. pp. 492. With a second 4to. Atlas of Plates. Paris, 1805. Imported by De Boffe. price 155.

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MONG a multitude of very short articles in this volume, we have been much gratified with the perusal of a few which are treated in a very ample manner, yet without superfluous minuteness. The subject of argillaceous earths is treated in two chapters, the first of which relates to their divisions and geognostic situation, and the second to their nature, properties, and uses. Of the difficulty of assigning precise characters to the multiplied varieties of clay, M. BROGNIART seems to have been sufficiently aware.

See Appendix to Monthly Review, Vol. 46. p. 465.

As, in

fact,

faet, it presents, in its natural state, no series of essential and constant marks, but only a mixture of different earths in variable proportions, it can never form a mineralogical species, according to the most received principles of modern arrangement. The alumina, which is essential to its designation, often exists, as Haiy has justly observed, in such a trifling proportion, that, in a method founded on chemical analysis, most of the stones denominated clays could not be classed under the title of aluminous. We may add that scarcely any two strata of argillaceous earth exactly resemble each other; and that striking differences sometimes occur even in the same stratum. In this state of embarrassment, the mineralogist is reduced to the necessity of limiting his descriptions to some of the most prominent varieties, which are distinguished by external appearances, by the places in which they occur, or by the uses to which they are applied in the arts. Assuming, as the general properties of clays, diffusibility and ductility in water, and induration in heat, we may thus distinguish them from mere schisti, which are not diffusible in water; from horn-stone, trapp, serpentine, and other stones of a dull, earthy fracture; which, however moistened with water, never form a paste; and lastly from chalks, which, though diffusible, are not ductile, in water, and are not susceptible of being hardened by heat.

M. BROGNIART distributes the principal varieties into apyrous, fusible, effervescent, and ochreous. The first in his first section is the Native Argil of Kirwan.

The real existence of this clay in nature (he says) has been called in question. It has been found at Halle, in Saxony, in small mamellated masses, disseminated in the uppermost layer of the soil. As it now very seldom occurs in this situation, and there is a large laboratory in the neighbourhood, some persons have suspected that it is a product of art: but Bönich, who supplied Fourcroy with specimens, has observed that the laboratory is at the distance of more than a kilometre (513 toises) from the spot at which the clay is found, and that a very high wall intervenes. Native Argil is likewise id to have been discovered at Magdeburg, in Lower Saxeny, in Silesia, at Potinier, near Verona, and in England. This clay is of a pure white, and meagre, though soft to the touch. When examined by the microscope, it appears to be composed (says Schreiber,) of a mul titude of small prismatic and transparent crystals, a character which does not belong to artificial alumina. It adheres strongly to the tongue, but does not form a paste with water, emits the argillaceous odour, and sometimes effervesces with acids. This last circumstance, according to Kirwan, proceeds not from the presence of an extraneous earth, but from the appropriate combination of the alumina with the carbonic acid. To the same cause, he ascribes its meagreness to the touch. Yet Theodore de Saussure assures us, from positive experiments,

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periments, that this clay contains no carbonic acid, a. d that alumina itself cannot be converted into the form of a solid carbonat.

Schreiber has found in this clay some particles of the carbonat and sulfat of lime, and of the sulfat of iron.'

The Collyrite variety is also rare, Friesleben found it at Weissenfels in Thuringia, and Dr. Townson at S hemnitz in Hungary. It is white, ductile, and very retentive of water; which squirts from it by pressure. It loses, by desiccation, half its weight, and separates into basaltic prisms, like starch. According to Klaproth, the Hungarian sort yields 45 parts alumina, 14 silica, and 42 water.

The pipe clays are here denominated plastic; and many of their varieties, especially those which occur in France, are particularized.

Among the fusible kinds is the Saponaceous, or Argilla Saponiformis of Werner, which is found at Okutsch in Poland, and in England, though very rarely. It is distinguished by its earthy and fine grained fracture, its soft and greasy feel, and its very strong adherence to the tongue.

Another remarkable variety has been termed the light. Its specific gravity, according to Fabroni, is 1,372, and sometimes only 0,362. It floats on water, when not imbibed by that Huid. That which Fabroni discovered near Santa Fiora, in the Siennese territory, and of which he made floating bricks, has been very improperly denominated fossil flour, and mineral agaric, which are popular names for certain varieties of the carbonat of lime, Fabrani's analysis of light clay is, Silica 55, magnesia 15, water 14, alumina 12, lime 3, iron 1.-Of this description of argillaceous earth, Faujas has discovered two subordinate varieties in the department of the Ardèche.

M. BROGNIART's remarks on the mineral situation of argillaceous earths are sufficiently conformable to the general state of facts; and his details with respect to the manufacture of bricks, tiles, earthenware, tobacco-pipes, &c. are likewise extremely judicious and satisfactory. A few paragraphs are allotted to the alcarazzas, or cooling vessels of Spain, Egypt, Syria, &c. M. Foureroy, of Paris, has succeeded in imparting a still lower temperature to water by employing a slightly baked porcelain of a coarse grained paste.-A long and distinct account is given of the china manufactory at Séves. Those of Vienna, Meissen, Frankenthal, Louisburg, Berlin, Copenha gen, St. Petersburg, Naples, Florence, and Madrid, are also mentioned, but no notice is taken of those of England.

The article Arsenic is likewise treated at some length. As this fossil substance occurs under various forms, and is even in, cluded