what he calls, an equivalent altitude; (altezza equivalente;) that is, an altitude, from which, if a body fell freely, it would acquire a velocity equal to that obferved in the water, at the furface of the river. This theory was highly approved by the Abbé Frifi, who confidered it as fatisfactory; and it has, with various modifications, been adopted by moft fpeculative writers on the subject. M. BRUNINGS juftly obferves, that the phenomena of water difcharged from the aperture of a veffel kept conftantly full, can be applicable to thofe rivers only which flow out of a lake, as the Adda, the Ticino, and the Mincio, in Italy; the Rhine, below the lake of Boden or Zeller, and the Rhone below that of Geneva: yet, even in these cafes, the analogy is imperfect. Water discharged from the aperture of a vellel flows freely, without any confinement, and without any refiftance, excepting what the air may offer to its courfe; whereas the water of a river flowing out of a lake, must be limited within a channel. That this circumftance greatly affects its velocity, is evident from the experiments of Poleni; who found that, when a channel was fixed to the aperture of a veffel, the quantity of water difcharged was confiderably augmented; and that this augmentation was increafed by the channel being lengthened to a certain degree, beyond which its prolongation had a contrary effect. Befide, with regard to the experiment itself, it is well known that, in order to make it confirm the law which it is intended to illuftrate, the aperture must bear a certain proportion to the capacity of the veffel; and if an inattention to this circumftance can vary the refult of an experiment fo fimple, with how little propriety can the theory founded on it be applied to rivers, which are fubject to innumerable varieties in this, and in many other refpects? Independently, however, of arguments drawn from a confideration of the hypothefes themfelves, on which this author infifts, it is certain that the theories hitherto invented, inftead of being confirmed, have been abfolutely contradicted by experiments made in natural rivers. The velocities of thefe, when measured at different diftances from the furface, have not been found to correfpond with any regular fcale; and, even at the furface, the computed velocity has often been between thirty and forty times greater than the real. Michelotti, and others, have endeavoured to difcover laws, by which these calculations may be corrected and applied to particular cafes, but without fuccefs; for though we fhould be able to affign the causes which render this real velocity of a river lefs than the computed, it is impoffible, á priori, to determine the degree in which they may act in every particular inftance. Mm 3 In In order to prove this point, M. BRUNINGS enters into a minute detail, and critical examination, of the experiments made by Zendrini, Lecchi, Lorgna, Michelotti, Ximenes, and other philofophers, which, fo far from confirming any theory, plainly evince the uncertainty of all. Hence he concludes, that no theory either has, or can be, difcovered, by which the velocity of rivers can be afcertained; and that, as this problem is purely phyfical, careful and accurate experiments are the only means by which its folution can be attained. In the third chapter, the author inquires what is the best inftrument for meafuring the velocity of a river at any given diftance from its furface. After defcribing those which have been used for this purpose, and fhewing their defects and inaccuracy, he propofes one of his own invention; which, as far as we can judge from his defcription, feems to be better contrived than any that has hitherto occurred to our observation. To give our readers a complete idea of it, without the affiftance of plates, is impoffible; we can therefore only inform them, that it is an improvement of the hydraulic balance, which, by means of a counterpoife, fhews the force with which. the ftream acts against a quadrangular brafs plate, that is made to flide on an upright beam, and may be fixed at any given depth. With a machine of this kind, for fome improvements of which M. BRUNINGS acknowleges himself indebted to the ingenious Mr. John Cuthbertion who conftructed it, several experiments were made in the Rhine, and the Yffel, which are here minutely related. This differtation is followed by a fhort memoir, containing fome obfervations on the flowers of the nutmeg-tree, written by Dr. HOUTTUYN, a phyfician in Amfterdam; who, fome years ago, publifhed a large work on natural history, in Dutch, in which he followed the fyftem of Linné. In the several defcriptions that have been given of this tree, little mention is made of the flowers. Munting defcribes it as bearing white bloffoms, like thofe of the cherry and pear-tree: but Dr. HOUTTUYN thinks that thefe are to be found only on the male, or wild nutmeg-tree, the fruit of which is of a very inferior quality, Rumphius afferts, that the female, or common nutmeg, proceeds from a white bell flower, like the lily of the valley. This defcription correfponds with the fpecimens received from Batavia: but both Dr. HoUTTUYN and Profeffor THUNDERG of Upfal, appear to have been uncertain concerning the fex of theie flowers. On a clofer infpection, with the microfcope, they are found to be hermaphrodites, and are to be referred to the clafs of the Gymnandria dodecandria. The The third article in this volume is a prize differtation, written by S. J. VAN GEUNS, then a ftudent of medicine at Harderwyk, containing an account of thofe vegetable productions of the United Provinces, the culture of which is worthy of peculiar attention, from their utility as articles of rural œconomy, or for the fake of their medicinal properties; or on account of their affording materials for arts and manufac tures. On all thefe accounts, the urtica dioecia, or great flinging nettle, is highly recommended. Not only is it faid to be excellent food for cows, and to improve the quality, as well as increase the quantity of their milk, but M. VAN GEUNS afferts, that it is an effectual prefervative against the contagious disease of the horned cattle, by which thofe beafts, that fed on it, were not at all attacked. The last memoir is an account of a new hyetometer, by M. CHRISTIAN BRUNINGS. After briefly enumerating the inconveniencies and inaccuracies attending the inftruments commonly used for meafuring the quantity of rain that falls in any given time, M. BRUNINGS defcribes one which was made, according to his direction, by Mr. Cuthbertfon, and is found, on trial, to be very accurate. It confifts of a funnel, the upper opening of which is exactly thirty-fix fquare inches, furnished with a ftrainer; through this ftrainer the rain paffes into a brafs veffel, of the form of a right-angled parallelopiped, the base of which measures twelve fquare inches; fo that a depth of three lines in this veffel, is equivalent to that of one line in the funnel. At the bottom of the parallelopiped, there is an open brass tube communicating with a barometer tube, in which the water rifes to its level in the veffel; and its height is pointed out by a fcale divided into inches and lines. Sow. 8vo. ART. IV. Verhandelingen, &c. i. e. Memoirs published by the Philofophical Society at Haarlem, Vol. XXVII. Part 1. pp. 170. Haarlem. 1789. THE HE greater part of this volume is devoted to metaphyfical difquifition. The ingenious M. MOSES MENDELSSOON, a learned Jew of Berlin, in a philofophical work published fome years ago, advanced, what he conceived to be, a new argument, deduced from the imperfection of our knowlege, to prove the existence of the Deity. For this purpose, he reasons in the following manner: Whatever is poffible, must be conceived and known to be poffible: and whatever exifts, must be perceived and known, as exifting, by fome intelligent Being. The human foul certainly exifts. It must, therefore, M m 4 therefore, be clearly and perfectly known to fome intelligent Being: but neither our understanding, nor that of any finite Being, is adequate to this knowlege. An infinite Intelligence must therefore exift. A critical examination of this argument having been propofed by the fociety as the fubject of a prize differtation, two memoirs concerning it are here published, the authors of which are GERRIT VANDER VOORT, Efq. Advocate in the Supreme Court of Holland, and the Rev. A. HULSHOFF, A. M. Minifter of the Baptifts in Amfterdam. To each of these gentlemen, a gold medal was awarded. Of thefe two differtations, M. VANDER VOORT's has the moft fcientific appearance: but we cannot help thinking M, HULSHOFF's more full, as well as more concife. The former of thefe gentlemen obferves, that the argument in question is by no means new; that the fame mode of reafoning has been ufed by M. De Pinto, another Jewish philofopher, in a work entitled, Precis des Arguments contre les Materialifes; and by Profeffor Garve, in his obfervations on Cicero de Officiis. He then proceeds to a minute examination of the major propofition, against which his objections are chiefly levelled; and, by inquiring into the precife meaning of every term, he expofes the fallacy of the whole. For this purpose, he makes use of the diftinétion between logical and hypothetical poffibility; and obferves, that, if the term poffible refer only to the former, the propofition may be granted: but, in this cafe, it does not affect the conclufion, as it amounts to no more than that whatever does not imply a contradiction, muft be conceived to be poffible: but if hypothetical poffibility be meant, the propofition cannot be allowed, without, at the fame time, fuppofing the exiftence of a Being which not only can, but, from its very conftitution, neceffarily muft, conceive whatever is poffible, and know whatever exifts. This condition renders the whole a mere petitio principii; for, in this cafe, the argument is founded on the very truth which it is intended to prove. M. HULSHOFF ufes nearly the fame mode of reafoning: but he enters into a more particular examination of the supposed neceffary connection between existence, and the perception of that exiftence. After obferving that, with regard to material objects, this connection was maintained by Berkeley, he oppofes to it a number of folid and judicious arguments, with which, as the fubject cannot be new to our metaphyfical readers, we fhall not detain them. With refpect to the minor propofition of M. MENDELSSOON's argument, the author juftly obferves, that, though our understanding is inadequate to the knowlege of the human foul, it by no means follows that this must be true true of every finite intelligence. There is, at leaft, no abfurdity in fuppofing that finite intelligent Beings may exist; endowed with powers and capacities fo greatly fuperior to those of man, that they may fully comprehend the nature and properties of the human foul; and, if this be poffible, we cannot deduce the existence of the Deity, merely from the circumftance of our own ignorance. The remaining article in this publication, is an account, by M. J. KRAGTINGH, furgeon in Haarlem, of a dreadful fracture in the arm, occafioned by its being intangled in the wheel of a water-mill. M. KRAGTINGH found it neceflary to amputate at the fhoulder joint. He defcribes the operation, which was performed in the manner directed by La Faye, the deltoides being preferved to cover the wound. The patient's death, which happened during the next day, is afcribed to the violent injury received by the accident. Sow. ART. V. Memoires Hiftoriques, Politiques, et Geographiques, des fea, with which the French miniftry flattered themselves, appears to have been the occafion of the prefent author's travels; in which his defign was to establish a commerce between France and Perfia. His chief object in writing these memoirs is to appeal to the public against Count de Choifeul Gouffier, ambaffador from Verfailles to the Ottoman Porte, and author of Les Voyages Pittorefque de la Gréce; of which we have given repeated accounts in former Reviews. As it would be unfair to offer any opinion concerning the merits of this difpute till the oppofite party is heard in defence, we fhall take no further notice of his account of this difference, than to obferve that it is highly incumbent on the ambaffador, if he would avoid the moft odious and dishonourable imputations, to produce full proofs of the invalidity of fome parts of the accufation, which may affect his character, not merely as a politician, but as a man of honour and integrity. The chief part of the first volume contains a defcription of Conftantinople, and a very general account of the government and state of the empire. The author then relates the declaration of war against the Ruffians, with the events which immediately preceded and followed this measure. On this occafion, he gives us fome anecdotes of Haffan Pacha, who, in addition |