Professor Wurzer, in a letter to Van Mons, mentions a singular phænomenon of detonation. To a solution of sulphat, of muriat, and acetite of soda, he accidentally added a crystal of nitrat of silver; a smart but slight detonation followed. He adds, that the salt'-we suppose the metallic salt-had been made three years before, and, during that time, had been exposed to the sun; which reminded us of the observation in a late collection of essays, of the phænomenon of the argentum fulminans having been occasioned by its previous exposure to light, in support of the idea of detonation arising from the mutual repulsion of heat and light.

M. Badolier's new method of preparing the Acetic Acid at one quarter of the usual expense, consists in distilling, with a gentle heat in a sand bath, with glass retort, &c. equal parts of sulphat of copper and acetite of lead. The acid is perfectly

pure.

Abstract of a Treatise on Vinegars, by M. Parmentier. The title to this article seems to require explanation. In reality, the treatise of which the account is here given occurs in the "Complete Course of Agriculture,' and is a very proper appendix to the Treatise on Wine by M. Chaptal. The manufacture of vinegar requires an increase of temperature, with a free exposure to the atmospheric air. Some additions, that act as a ferment, are also requisite, which in this country the stalks of raisins often supply; and a certain proportion of alcohol is equally necessary to avoid mouldiness and putrefaction. The author next describes the different management for different sorts of vinegar, and particularly mentions that from cider, perry, beer, and the bran of wheat. He next enumerates the vegetable acids substituted for vinegar, particularly those of gooseberries, barberries, &c. The means of preserving vinegar are next noticed. By evaporating the water, the flavour is lost; and, even when concentrated by frost, the acid acquires a disagreeable smell and taste, which the author calls, somewhat improperly, empyreumatic. Sea-salt added will often for a time succeed. The adulterations of vinegar, and its imperfect states, are next adverted to; but on this point we find nothing which merits our notice. A very slight knowledge of chemistry will supply all that the author suggests.

New Experiments on the Galvanic Fluid, by Robertson, read to the National Institute.' This article is of no great importance. The author thinks the Galvanic power to be very different from electrical, and that the influence is that of an acid.

Analysis of the white silvery Chlorite, by M. Vauquelin.' This species of chlorite is soft to the touch, formed of little brilliant scales, and possessed of the smell of clay when moistened. Its substance is however chiefly siliceous, with about 0.018 of

alumine. It differs however from the green chlorite, crystallised in prisms, by containing a little pot-ash; while the latter contains magnesia, which the white does not furnish in the smallest quantity. Our author therefore would separate the green and white kinds; but we should have considered his determination as too rigorously chemical, did not its more obvious properties, the form of its crystals, coincide in the same result.

Experiments relative to the Action of Sulphurated Hydrogen on Iron, by which it is said to form the Muriatic Acid, by M. Vauquelin. Our author, in repeating the experiment, found no muriatic acid; and he suspects the ingredients to have been impure when the acid was observed. It appears, from the experiments of Berthollet, that iron, recently filed, shows no traces of this acid; but, after a slight exposure to the air, it may be discovered. This will not be surprising to those who, with Margraaf and others, have found this acid in condensed dew and frost. In this experiment, much hydrogenous gas was emitted, which could not, in M. Vauquelin's opinion, arise from the sulphurated hydrogen; since, to combine with the sulphur, the metal must be previously oxygenated. He supposes therefore that it decomposes a part of the water, attracting first its oxygen, and then the sulphur; increasing, by both operations, the quantity of hydrogenous gas emitted.

M. Áchard found that seeds germinated much sooner, and animals lived longer, in condensed air. When the air was condensed three-fold, animals lived five times longer. When suddenly condensed, they sunk with all the appearances of compression on the brain. Birds let loose from condensed air seemed to experience no inconvenience from the comparative rarity of common air.

A Memoir on different Kinds of Mortars, on poor Lime, on Tarras, and on Puozzolane, by M. Guyton.' This author describes the composition of different kinds of mortars invented or recommended by chemical writers, and then speaks of poor lime, which is so called, from its not producing a mortar equally rich with that procured from the other kinds. Its useful property is however that of hardening in water, which it owes to a portion of manganese. It contains also a small portion of clay; and M. Guyton thinks that it may be prepared artificially, by adding to ninety parts of good powdered limestone, four of clay, and six of manganese. The methods of making tarras are next noticed; and puozzolane may be supplied, in the author's opinion, by basaltes heated to a red heat, then thrown into water, and sifted when dried. M. Monge visited the remains of Cæsarea (Cæsarea Stratonis), and could distinguish the different ages of the buildings by the solidity of the mortars. In one part there were beautiful ornaments en

creux, formed by what had been executed in relief in stone. The latter was decayed, but the mortar continued unchanged.

'Memoir of M. Pontier on the Manufacture of Saccharum Saturni, read at the Session of the Mines: abridged by M. Vauquelin.' For many years the acetite of lead was supplied by Holland, and the preparation kept secret. It has been long made in France, and the process is in general known: M. Pontier describes it with care, and has added some important improvements. The chemical reasoning is deferred to another memoir; and a minute process cannot be abridged.

Experiments and Observations on some Philosophical and Chemical Phænomena which the Electrical (the Galvanic) Apparatus of Volta presents, by M. Desormes.' The article before us contains chiefly experiments which we cannot curtail; but it also contains some observations, of which we shall offer a short abstract. The principle of Galvanism appears from these experiments-and this indeed has been often remarked before-to consist in the oxydation of the metal; and the electricity on the oxydated side is positive. It does not arise, in M. Desormes' opinion, from the decomposition of the water; and the force of the apparatus has little influence on the oxydation beyond a certain point. But the electricity (for thus he styles the Galvanic fluid), though not produced by the decomposition of the water, will afterwards, by its own power, effect this change. The author next notices the order of the metals and the fluids which will produce the greatest effect; and points out some well-known phænomena, which we need not stay to describe. He repeats the English experiments on the proportion of the airs, and the formation of acid and alkali on the oxydating or hydrogenating sides. In illustration of this fact, the author notices a remark of Vauquelin, who, on triturating rock crystal in an agate mortar with syrup of violets, found the syrup assume a green colour. The author, on farther inquiry, found that, when the same substances were rubbed together, that which was bruised and had its polish destroyed exhibited an electricity contrary to its natural inclination. As that of rock crystal is positive, the electricity which rendered the syrup green must be negative. We remember Dr. Cullen making a similar observation thirty years since, when speaking of the preparation of the unguentum mercuriale. He attributed the calcination of the metal to the electricity excited by the friction, which, (he added) in many cases, appears to perform the office of an acid. We mention it as a proof of singular sagacity; nor was it the only one. Some remarks on the oxydation and reduction of metals by the electric fluid, follow. The augmentation of the pile appears to have no effect in increasing the oxydation.

Reflexions on some Passages in ancient Authors, by M.

Pissis. This is an excellent little paper, and draws the balance between Mayow and his contemporaries with great judgement. The author shows that Mayow was, as we have already observed, noticed by them, particularly by Hales and Baglivi; but the preponderance of Hales's credit obscured that of Mayow; and Baglivi's theory of the loss of elasticity was considered as a more satisfactory theory than the loss of the nitrous aërial spirit. The connexion of the loss of elasticity with the loss of caloric, though not known to Hales, was hinted at by Seneca, who however cannot pretend, as some hasty undistinguishing inquirers have supposed with respect to Mayow, to have anticipated every modern discovery.

ART. IV.-Mémoires de l'Institut National des Sciences et des Arts. Memoirs of the National Institute of Sciences and Arts. (Continued from Vol. XXXIII. p. 486.)

OUR last article commenced with the second volume of the class of Moral and Political Sciences; and we advanced to Memoir VI. inclusively. We now continue our analysis, which will include the remainder of the volume.

VII. On the State of the French Marine at the Beginning of the Fourteenth Century, and on the Kind of Tactics at that Time employed in Sea-Fights. By M. Legrand d'Aussy.'

This memoir is altogether drawn from a poem, or rather a history in rhyme, of an engagement in the year 1304 on the Zealand coast, between Guy de Namur, count of Flanders, who had usurped great part of the territory of Jean d'Avènes, count of Holland and Hainaut, and the French fleet, under the command of Renier Grimaud (Grimaldi) a Genoese captain, or rather corsair, of great courage and reputation, who was enticed into the service of the French marine by Philip the Fair, at that time engaged in a war against Flanders, and consequently a close and powerful ally of the count of Holland. The period of the battle comprises about sixteen hours, and extends through an entire night. In the ensuing morning, the combatants manifest a double degree of vigour; and, in the issue, Guy de Namur is taken prisoner amidst a prodigious slaughter of his own forces; and the victory of course is amply decided in favour of Grimaldi. This historical poem was written by Guillaume Guiart, a native of Orléans, and was fantastically entitled Branche aux Royaux Lignages. Its versification is totally destitute of merit; but its descriptions appear to be accurate; and the only use which is made of it in the present instance, is to convey some idea of the naval tactics of the century referred to. Prior to the æra of Francis I. the French

had no established marine whatever, nor even conceived the necessity of such an establishment. As the forests of Germany were infested with vast bodies of banditti, the seas were in like manner infested with vagrant fleets of corsairs, several of which frequently united themselves under the command of one intrepid and celebrated chief; and their services were to be hired by any power who meditated a descent on a neighbouring territory, or who in any other way stood in need of naval assistance. The present French and Flemish fleets were, for the most part, composed of such detached and independent squadrons; and in their attack and defence they retained much of the old Roman mode of combating. Vessels of every description, large and small, ships, galleys, boats, were all brought into action at one time: the larger were laced together for mutual support, and to prevent the possibility of their separation. They were lined on the decks with a promiscuous crowd of archers, slingers, and swordsmen; while strong and gradually diminishing stages or platforms surrounded the masts at different heights, loaded with slingers and bowmen alone and for the defence both of the deck and platforms, or turrets, as they might more properly be called, a breast-work was thrown around of a kind of sail-cloth, which obviously afforded protection rather by concealment than resistance. Every ship thus manned resembled an oriental pagoda; and, in some instances, the turrets constructed around the masts were so lofty as to give the body of troops there situated a full command of the walls about to be assaulted, and an opportunity of employing their catapults against the interior of the fort or city. This mode of assault was by no means unknown to the ancient Romans. It was adopted, as most of our readers will recollect, on a wonderfully extensive scale, by Marcellus, during the siege of Syracuse; at which time nothing but the superior skill of Archimedes preserved the city from the destruction that was menaced. We do not find, however,-and it is almost the only deviation we have observed from the instruments introduced into the Roman marine,--any notice taken of the corvus Duillii, or machine invented by the consul of that name, for the purpose of boarding; of which we have given a brief account in our review of M. Le Roi's Memoir*, respecting the advantages to be derived from the re-adoption of that instrument, as well as of several other facts and circumstances common to the naval establishment of that celebrated republic. We may naturally therefore conclude, that, notwithstanding the praises lavished upon ít by several historians, it was found too cumberous and inconvenient for general utility, and was, in consequence, gradually relinquished.

* See our 31st volume, p. 497.