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acknowlege the merit of a foreigner; and that, on the present occasion, besides allowing all the due share of praise to the immediate subject of his memoir, he takes occasion to render justice to Scheele, Priestley, and others, who, about the same period, were engaged in the same train of pursuits.

The first Memoir in this department is by M. RICHARD, On the Hydrocharides; i. e. on the Plants which, with the Hydrocharis, constitute the natural Family of this Name. Our readers must be aware of the fondness which the French botanists manifest for the plan of forming natural families; a plan which, if cautiously pursued, is well calculated to promote botanical science, but which, on many occasions, they have certainly carried to an unreasonable extent. We will not decide whether this remark applies to the case now before us: but we are disposed to think that, although the plants placed together, as forming one natural division, have some common points of resemblance, they are very dissimilar in many essential parts. The essay is extremely elaborate, being extended through 88 4to. pages; and indeed it seems to contain every thing essential to the complete investigation of the subject. The plants which are classed under the title of the Hydrocharides are the Elodea Guyannensis, which is little known, and which grows in Guiana, as its specific name imports; the Anacharis Callitrichoides, which was discovered by Commerson, near Monte Video; Hydrilla ovalifolia, an Indian plant described by Roxburgh; Vallisneria spiralis, an European dioecious plant; Blyxa Auberti, also a diœcious plant, discovered by M. Aubert du Petit Thouars, at Madagascar; Blyxa Roxburgi, a native of Coromandel; Stratiotes aloides, a well-known European plant; Ottelia Alismoides, an inhabitant of the Nile, near Rosetta, and perhaps also of India; Limnobium Bosci, a native of South Carolina, where it was discovered by M. Bosc, after whom it is named; and, lastly, the Hydrocharis Morsus-Rana, a common and well known inhabitant of various parts of Europe, which on this account gives its name to the whole family. After a minute scientific description of each of these plants individually, the author makes some observations on the family generally, their habits, their different parts, and their various organs. The characters are given in Latin, arranged into orders and genera; and a conspectus of the whole is added, together with a series of engravings. To the memoir is subjoined a description, with a figure, of the plant generally known in medicine under the title of Angustura, but now named Bonplandia.

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The next paper is a Continuation of M. GUYTON-MORVEAU'S Essay on Pyrometry; the principal object of which is

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to make a correct estimate of the real value of Wedgwood's table of temperatures, as taken from his experiments with the clay-thermometer. The author conceives it to be an instrument of considerable merit, but he thinks that the values assigned by Mr. Wedgwood himself are extremely erroneous. It will not be seen without surprize,' he observes, that the 1077th degree of the thermometer of Fahrenheit, which, according to Wedgwood, answers to the zero of his own pyrometer, is found here replaced by 517°; and that the value of 130° of Fahrenheit, which he has assigned to each: of the divisions of his pyrometric-gage, are here reduced to 621°; which, admitting an uniform progression in the highest temperatures, does not carry the temperature of melted iron, for example, to more than 8696o of Fahrenheit, instead of 17327, and consequently to 4609° of the centigrade ther mometer, instead of 9606°. This error appears to have originated in Mr. Wedgwood having formed a wrong estimate of the melting point of silver, which he made one of the principal data for connecting his scale with that of the mercurial thermometer. In rectifying the temperatures of that gentleman's pyrometer, and comparing them with those of the mercurial scale, the present author employs as an intermedium the pyrometer of platina; and, in order to connect this with the two points of the freezing and boiling of water, (which are the points on the mercurial scale that are the best established, and to which the rest are generally referred,) he employs some more dilatable metals; as also the vegetable oils, the boiling point of which is so much higher than that of water. The paper, generally speaking, seems to us of considerable value, and to deserve the attentive examination of those who are interested in ascertaining with accuracy the higher degrees of temperature. It is accompanied by some tables containing the numbers that, result from the writer's experiments.

Observations on the Arrangement and Disposition of Leaves, on the Medulla of Ligneous Vegetables, and on the Conversion of the Cortical Strata into Wood. By M. PALISOT, Baron de BEAUVOIS. The author enters very fully into this subject, and considers every part of it with minuteness. With respect to the medulla, he inquires into the nature of its substance; the form of its mass, or that of the case in which it is inclosed; the changes which it experiences; and lastly its use. All these points form the topics of so many separate sections, in which he examines the opinions of Malpighi, Hales, Grew, Duhamel, and other preceding writers, and afterward gives his own ideas concerning them. As the use of the medulla has been much controverted, we shall quote the present observations on it: If we cannot conclude that the medulla is M m 3

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an organ necessary to the increase and developement of vegetables, that it has always a real use, viz. as Grew advanced, direct and immediate in the first year, and as long as the medullary canal is charged with fluid and remains succulent, -it appears at least probable that it has an indirect and mediate action when, being grown dry, without strength and power, it cannot act but by the intervention of its radii, which communicate directly with it, and are a continuation of it.' With respect to the action of these radii, it is supposed that they are connected with the leaves or young branches of the stem; so that, according to its shape and number of projecting parts, the branches grow out in pairs, or in some other number, radiating from one part. Of these forms there are said to be five; triangular, when the leaves grow out three together; tetragonal, when the leaves grow in sets of four; pentagonal, when they are disposed in sets of five; and round or oval, when the leaves are placed in pairs. With respect to the conversion of the cortical strata into new wood, the author remarks that one point which he has established is to demonstrate that the opinion of Malpighi, Grew, and Duhamel is correct, that the new woody strata are produced by the liber, and not, according to the opinion of Hales, from the previously formed wood,' or, as it is termed, alburnum..

In a second memoir, M. PALISOr brings forwards additional proof of his opinion respecting the arrangement of the leaves; and he observes that, in all the plants with whorled leaves, the form of the medullary sheath is always in harmony with the number, arrangement, and disposition of the branches. These memoirs are accompanied by some illustrative plates.

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Vol. XIII. for 1812.*-MATHEMATICS AND ASTRONOMY.

The historical part, by M. DELAMBRE (as usual,) begins with an account of the memoir of M. Legendre on the attraction of Homogeneous Spheroids, to which he was led in consequence of the simplification that Mr. Ivory had given to this kind of investigation. The Secretary next examines, in some detail, the memoir of M. Poisson which we have noticed in a preceding page (527.); he then gives a slight sketch of seven different papers by M. Rochon; adverts to the lunar tables of M. Burckhardt; passes in review several works, among which are Laplace's Analytical Theory of Probabilities, Carnot on the Defence of fortified Places, and other new editions of old works; and with these he concludes the historical preliminary.

*In the second part of this volume, the epithet Imperial, before given to the Institute, is omitted, and no other substituted.

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In the succeeding article, the Secretary supplies notices of the lives of Malus and Lagrange; of the latter of whom we have already spoken in our report of his Mécanique Analytique, and respecting the former we shall merely transcribe one sentence: Newton, speaking of a young friend whom he had lost, said, "If Cotes had lived, we should have known something" and we may, in like manner, say, If Malus had lived, he would have completed the theory of light.' This celebrated philosopher, whose name will be transmitted to the end of time in consequence of his discovery of the polarization of light, died on the 24th of February 1812, in the 37th year of his age, and was replaced in the Institute by M. Poisson; who is well worthy to succeed him.

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(Part I.) MEMOIRS. On a new Kind of Oscillation which the Particles of Light experience in traversing certain Crystals. By M. BIOT.

(Part II.)

On a new Application of the Theory of the Oscillations of Light. By the Same.

On the Discovery of a new Property in the polarizing Forces of certain Crystals. By the Same.

On the Physical Properties that the Particles of Light acquire in traversing double refracting Crystals. By the Same.

These memoirs occupy more than 400 pages, and are crowded with numerous experiments and ingenious deductions; which, as we have before remarked in reference to this author's paper in the preceding volume, bid defiance to any intelligible condensation. We must consequently pass over them with the mere enumeration of their titles.

Result of the Meteorological Observations made at ClermontFerrand, from the Month of June 1806, to the End of 1813. By the Baron RAMOND. On examining the dates in the title to this memoir and the title of the volume itself, it will be found that the article which is here said to be inserted in the volume for 1812 was not written, and the experiments which it details were not finished, till 1813; that it was not read till 1814; and that it was not published till 1816. We cannot but remark the impropriety of thus giving an apparent earlier date to papers than the period at which they were written. Let us imagine such a case as the invention of fluxions by an Englishman in 1813, which is mentioned to a few friends, and arrives by some means at Paris in 1814; let us farther imagine a foreigner so lost to all sense of honour as to appropriate to himself that which he knows, and he almost exclusively, to belong to another; of which we will suppose him to present an account to the Institute in the latter end of this year; and the memoir to be then pub

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lished in the volume for 1812. Some years afterward, a dispute shall arise concerning priority of invention; the Englishman, and his friends, trace the date of the discovery to the year 1813; while the Frenchman, and his friends, prove that it was published in the volume of their Institute for 1812, and consequently that the latter has a priority of claim. We beg most positively to state that, in putting the above case, we by no means intend to imply the probability of such a transaction, but merely to shew the possibility of it, and thence to manifest the impropriety of the practice in question.—With regard to the memoir which has given rise to this remark, we must observe that it appears to contain very correct meteorological tables and observations; which, however, would furnish no useful information in a detached form.

On Elastic Surfaces. By M. PoISSON. This is perhaps one of the most difficult problems in mechanics. The labours of the mathematicians of the last century had apparently given to this doctrine all the extension, and every degree of perfection, of which it seemed possible: but this was far from being the case; and many problems still remain to exercise the talents and humble the pride of philosophers, among which the subject of the present article is not one of the least important. The differential equations of these surfaces in equilibrium, and à fortiori those of their motion, are not yet known; except in the particular instance of a cylindrical surface, which returns to the simple case of an elastic lamina. James Bernouilli was the first who gave the equation of the equilibrium of an elastic lamina; founding it on the hypothesis that the elasticity at every point is a force perpendicular to the curve, of which the moment is proportional to the angle of deflection, or in the inverse ratio of the radius of curvature at that point. Since this great geometer, many others, and principally Euler and D. Bernouilli, have published several memoirs relative to the conditions of the equilibrium of elastic lines, and on the laws of their vibration: but nothing in any respect satisfactory has yet been effected with regard to elastic planes; and even the present memoir, though bearing strong traces of the very powerful genius of the author, appears still to leave much to be desired in the solution of this delicate problem.

(Part II) PHYSICS.

In the history of this class by M. CUVIER, the learned Secretary commences by noticing the well known experiments of Count Rumford, on the proportional quantities of Heat extricated during the combustion of various bodies, and makes the

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