acts upon, and perhaps always electrifies, more or lefs, univerfal Nature, is one diftinct element, to which a diverfity of modifications gives different properties and effects, that its principal and vifible fource, with refpect to us, is the SUN, which, turning upon its axis, performs the functions of an electrical globe, and fends forth ftreams and torrents of that elementary fire, that is the great, active and vital fpring of life and motion. -This is an ingenious improvement of Boerhave's theory..

In the 2d SECTION, which is ftill more curious, the learned Abbé confiders the elementary fire, in the great phenomena of Nature, which it produces, in its modification, as an electrical fluid. He begins by pointing out its operations and effects on terreftrial bodies, and fhewing the part which the electrical fluid acts in animal fenfation, in the vegetation, mechanism and reproduction or renovation of animal and vegetable substances, in the formation and developement of meteors, and in many other terreftrial phenomena, that come perpetually under our obfervation. His comparison between this fluid, and that which anatomifts call the animal fpirits, from whofe action our sensations and motions arife, is certainly ingenious, and the analogy between the animal and the electrical fluids appears to him fo entire and perfect, that he attributes them, without difficulty, to the fame principle. Here alfo, he finds the point of communication and union between the foul and body, which, notwithstanding the fimplicity of the one, and the compound nature of the other, must have fome mean of communication; because of this communication, and of their real and reciprocal action in each other, we have an intuitive, irrefiftible and continual confciousness, which is the highest kind of evidence. The learned Academician has treated at great length, the important and curious fubject of this fection in a large work, bearing this title, THE METAPHYSICAL PRINCIPLES OF BEINGS (principes metaphyfiques des etres), and which he propofes to publifh fome time hence. This confiderable work will naturally excite an impatient curiofity. With refpect, however, to the analogy between the electrical and animal fluids, we think it is prefented in a very ingenious and plaufible manner, from various points of comparifon, in the Memoir now before us.

In Section III. the elementary fire is confidered, by our Author, in its operation in the higher regions, and in the celestial phenomena. Here, in proportion as the Abbè afcends, he gets into the region of conjectures; but as he proceeds with equal circumfpection and courage in this vaft region, we have followed him with great pleasure, and found him an entertaining and inftructive guide. The aurora borealis is the firft phenomenon confidered in this fection. Our Author fhews, that the accounts given of the causes of this phenomenon by Mairan, Hell,

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and other writers of note, are unfatisfactory, and that they contradict the most palpable facts, and the most accurate obfervations. He proves, by the moft conclufive arguments, that it is produced neither by the zodiacal light, nor by fermenting exhalations that take fire in the atmosphere, nor from the refraction or reflexion of the rays of the fun or moon falling upon the fnow or the icy clouds of the north. He brings many ingenious arguments, and offers a multitude of obfervations, to prove that this meteor, in its appearances in the Polar regions, both northern and fouthern, is nothing more than an emission of the electrical fluid, which difengages itself from the earth, and afcends in the atmosphere (in thofe parts of the earth that are opposite to the fun) in a rectilinear direction; and he alfo endeavours to prove, that this electrical emission is caused by a fuperabundance of heat received by thefe oppofite parts, which, according to the known laws of electricity, give them the quality of conductors.

Comets, and their tails, come next into confideration. The tails of these great and luminous bodies having a manifeft analogy to the aurora borealis, the learned Academician closely follows this analogy in all its reipects; and fhews, by unanfwerable arguments, that it is complete and perfect. From hence he concludes, that the aurora borealis and the tail of the comet proceed from the fame principle, and are formed of the fame matter; that they are emanations of the electrical fluid from their respective bodies, and that this fluid often becomes a phlogifton by the heterogeneous mixtures, which it carries along with it in this emanation, which accounts for the different colours and other circumftances obfervable in these meteors. As electrics (fays he), when fufficiently heated, become conductors of the electrical fluid, and yield emanations of it in proportion to the quantity they naturally contain, this is precifely the cafe with the earth and the comets in their perihelia. The ap-. proach of the comets to the fun, and the fuperabundant degree of heat, which they receive from this approach, dispose them to fend forth a proportionable part of their electrical fluid, whofe emiffion produces all the phenomena we obferve in the tails of comets, the aurora boreales, and feveral electrical experiments. These phenomena, therefore, have the fame caufe and one common principle. In the recefs of the comet and its increafing distance from the fun, this vifible emiffion of electrical matter diminishes gradually, and at laft totally disappears, and instead of being an electrical conductor, which it was in its perihelion, it attracts the fluid, is charged with it anew, and thus becomes electric, until its approach to the fun, and the heat it acquires thereby, change it again into a conductor.

As we cannot follow our learned Academician through all the details into which he enters in the difcuffion of this curious part

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of his fubject, we fhall only obferve, that, from the prodigious activity of the electrical fluid, its tendency to escape from the bodies which contain it, and to diffuse itself in the vaft planetary regions, which come the nearest to void space, he draws fome conjectures relative to the uses and the end which comets may ferve in the planetary fyftem. His conjectures amount to this: that comets are real electrical bodies, defigned to collect the electrical fluid, which has efcaped from the planets;-that these comets, heated by their approximation to the fun, communicate this fluid anew to the planets, and thus the perpetual circulation of this active fluid, fo neceffary to the great whole, is maintained and renewed inceffantly;-and that the operations of Nature in the planetary fyftem, are carried on in a manner analagous to what we conftantly obferve and experience in the perpetual circulations of our atmosphere, where winds, vapours, and exhalations rife and float, then return to us in rain, fnow, or fulminating explofions, and again are exhaled and raised anew. Every thing (fays our Author, and we are perfuaded that he fays the truth) is analogous and harmonical in univerfal Nature.

An ANALYTICAL ESSAY on the mechanism of Vaults. By the CHEVALIER DE NIEUPORT, Commander of the order of Malta, &c. This elaborate piece, which contains 89 pages, requires the infpection of the plates.

A MEMOIR concerning the curves, defcribed by a Body approaching to, or receding from, (in a given ratio) a Point which proceeds in a right line. By the fame.

Memoir concerning the method of finding a Factor, which will render a differential Equation complete, when this Factor must be the product of Two Functions, each of which contains only One variable Quantity. By the fame.

Memoir concerning the Natural History of the North-Sea *, and the fisheries carried on in it. By the Abbé MANN. In the firft fection of this ample Memoir, the laborious and learned Academician confiders the limits of the North-fea, its form, its ancient and modern denominations, its fituation with refpect to other feas, and to the countries adjacent; its forms, their duration, velocity, force, and the natural caufes of their direction; its climate, icy accumulations, depth, &c.

In the fecond fection he treats of the tides and currents of the North-fea. Here, after confidering the laws of motion, that regulate the direction of fluids, he treats of the direction of

* By the North-fea, our Academician understands that part of the ocean which is comprehended between the eastern coafts of GreatBritain, from Dover to the islands of Shetland on the one fide, and the oppofite or western coals of Norway, Denmark, and the Netherlands as far as Calais, on the other.

the

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the tides in general, and of thofe, more particularly, which come from the northern ocean * into the North fea, and by their direction from north-eaft to fouth-weft, enter partly into that fea, and partly into the Atlantic, by the north of Scotland and Ireland. This direction our Author deduces from the following principle, that the tides of the ocean, in consequence of the gravitation of its waters towards the moon, take naturally their courfe from north-eaft to fouth-weft in those parts of the ocean that are to the north of that planet, and from fouth-eaft to north weft in those that are to the fouth. The application of this principle to the courfe of the tides, and the irregularity and different directions of the coafts from whence the tides are reflected (according to the law of equality between the angles of incidence and reflection) account for the formation of currents, fandbanks, &c. and open a field of difcuffion in which the learned Abbé expatiates, and in which we are forry that we cannot follow him. We are perfuaded that .geographers and navigators will read with fingular pleasure his principles, combinations, and conclufions, which feem to be the refult of long obfervation and study. His theories are confirmed by the Marine charts and Atlaffes, both Dutch and English, which he appreriates with judgment in this fection.

The third fection relates to the fand banks and fhoals of the North-fea, and the local changes that have been produced in it, by forms and other natural causes. The objects of difcuffion in this fection are, the formation of fand-banks in the interior of the North-fea, and the reasons why they do not gradually increase in fize the formation of banks near the coafts-the effects and re-action of the banks already formed upon the tides and currents-the changes which the fand-banks and the bottom of the North-fea undergo-the fand-banks in other feas, which differ in kind from those of the North-fea, and are owing to different causes.

The natural Productions of the North-Sea, its fifberies, and the methods of improving them, are the fubjects of the fourth fection; which commences with a general account of the vegetable and animal productions of the North-fea, and of the authors who have defcribed them. This is followed by ample lifts of its fith, fheil-fish, aquatic birds, and plants. Our Author's account of the herrings, their different kinds, and their voyages, his particular remarks on the various forts of fifh contained in this fea, and immenfe gain which might be made by putting the fileries on a proper footing, are curious and interefting.

* That is, from that part of the ocean which lies between the Artic pole and the coafts of Siberia, Nova Zembla, Lapland, and Norway.

But nothing is more worthy of attention than his inquiry into the causes of the diminution of the number of fish in the Northfea, and more efpecially on the Dutch and Flemish coafts, during these last 25 years; a fact which is afcertained by the unanimous accounts of those employed in the fisheries. He attributes this diminution to three caufes, of which the two first are phyfical: the first is the fea's having loft a part of its fertility, and of the aliment which is neceffary for fish. As in certain lands, the force of vegetation and the nutritive juices seem to fail and decline at certain intervals, the fea alfo may lofe a part of that fertility which is peculiar to its bottom; and what seems to prove, fays our Academician, that this is really the cafe, is the fmall quantity of marine plants and productions, that is at present caft by the fea on the Flemish coasts, in comparison with what there was about 18 years ago, and this quantity, as the Abbé MANN affirms from ocular obfervation, diminishes from year to year. Now, it is well known, that these marine plants and productions are the habitations of different kinds of infects and worms, which nourish the fmall fifh; as alfo that these latter contribute to the nourishment and fubfiftence of the larger kinds, and that thus when any clafs of the finny tribe decays for want of food or fhelter, the reft must be affected by this decay: not to mention, that the immense quantity of fhrimps and other small fish that are taken and confumed on the coafts of Flanders, may also contribute to the diminution in question.A fecond cause of the diminution of the number of fish on the coafts of the Netherlands, is alledged modeftly by our Author, not as afcertained, but as a matter of probable conjecture; it is the earthquake, that deftroyed a great part of the city of Lifbon in 1755. This was felt all along the Flemish coaft, where the agitation of the waters was fo great as to drive the ships from their moorings. The line of direction that the fhock of this earthquake followed in the Northfea, was the coaft already mentioned; and it is natural to fuppofe (fays our Abbé) that this fhock may have been attended with fulphureous or bituminous eruptions, which may have left in the bottom of the fea fome pernicious or difagreeable quality, adapted to fpoil or diminish the nourishment of the fifh. But a more palpable circumftance that not only may, but mufi have contributed to the event complained of, is the manner of fishing that has been practifed, thefe 2 years paft, on the Flemish coafts, in oppofition to the numerous edicts of the fovereign. This manner our Academician describes in all its kinds, fhews its pernicious confequences, and points out the meaiures that he thinks proper to prevent the growing evil.

This curious Memoir is the fifth that has been compofed by the Abbé MANN, on the Natural Hiftory of the Netherlands,

and