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acts upon, and perhaps always electrifies, more or less, universal Nature, is one distinct element, to which a diversity of modifications gives different properties and effects, that its principal and visible source, with respect to us, is the Sun, which, turning upon its axis, performs the functions of an electrical globe, and sends forth ftreams and torrents of that elementary fire, that is the great, active and vital spring of life and motion. This is an ingenious improvement of Boerhave's theory.
In the 2d SECTION, which is still more curious, the learned Abbé confiders the elementary fire, in the great phenomena of Nature, which it produces, in its modification, as an electrical Auid. He begins by pointing out its operations and effects on terrestrial bodies, and iewing the part which the electrical Auid acts in animal sensation, in the vegetation, mechanism and reproduction or renovation of animal and vegetable substances, in the formation and developement of meteors, and in many other terrestrial phenomena, that come perpetually under our obfervation. His comparison between this fluid, and that which anatomists call the aniinal spirits, from whose action our sensations and motions arise, is certainly ingenious, and the analogy between the animal and the ele&trical Auids appears to him so entire and perfect, that he attributes them, without difficulty, to the fame principle. Here also, he finds the point of communication and union between the soul and body, which, notwithstanding the fimplicity of the one, and the compound nature of the other, must have some mean of communication ; because of this com, munication, and of their real and reciprocal action in each other, we have an intuitive, irresistible and continual consciousness, which is the highest kind of evidence. The learned Academician has treated at great length, the important and curious subject of this section in a large work, bearing this title, The MetaPHYSICAL PRINCIPLES of Beings (principes metaphysiques des etres), and which he proposes to publish fome time hence. This considerable work will naturally excite an impatient curiosity, With respect, however, to the analogy between the electrical and animal fluids, we think it is presented in a very ingenious and plausible manner, from various points of comparison, in the Memoir now before us.
In Section III, the elementary fire is considered, by our Aue thor, in its operation in the higher regions, and in the celestial phe. nomena. Here, in proportion as the Abbè ascends, he gets into the region of conjectures ; but as he proceeds with equal circumspection and courage in this vast region, we have followed him with great pleasure, and found him an entertaining and instructive guide. The aurora borealis is the first phenomenon considered in this section. Our Author shews, that the acfounts given of the causes of this phenomenon by Mairan, Hell,
and other writers of note, are unsatisfactory, and that they contradict the most palpable facts, and the most accurate observations. He proves, by the most conclusive 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 sun or moon falling upon the snow or the icy clouds of the north. He brings many ingenious arguments, and offers a multitude of observations, to prove
that this meteor, in its appearances in the Polar regions, both northern and southern, is nothing more than an emission of the elektrical fluid, which disengages itself from the earth, and afcends in the atmosphere (in those parts of the earth that are opposite to the sun) in a rectilinear direction; and he also endeavours to prove, that this electrical emission is caused by a superabundance of heat received by these opposite parts, which, according to the known laws of electricity, give them the quality of conductors.
Comets, and their tails, come next into consideration. The tails of these great and luminous bodies having a manifest analogy to the aurora borealis, the learned Academician closely follows this analogy in all its reipects; and thews, 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 same principle, and are formed of the same matter; that they are emanations of the electrical Auid from their respective bodies, and that this Auid often becomes a phiogiston by the heterogeneous mixtures, which it carries along with it in this emanation, which accounts for the different colours and other circumltances observable in these meteors. As electrics (says he), when sufficiently heated, become conductors of the electrical fiuid, and yield emanations of it in proportion to the quantity they naturally contain, this is precisely the case with the earth and the comets in their perihelia. The approach of the comets to the fun, and the superabundant degree of heat, which they receive from this approach, dispose them to send forth a proportionable part of their electrical fluid, whose emiffion produces all the phenomena we observe in the tails of comets, the aurora boreales, and several electrical experiments. These phenomena, therefore, have the same cause and one common principle. In the recels of the comet and its increasing distance from the sun, this visible emillion of electrical matter diminishes gradually, and at last 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 discussion of this curious part
of of his subject, we shall only observe, that, from the prodigious activity of the electrical Auid, its tendency to escape from the bodies which contain it, and to diffuse itself in the vast planetary regions, which come the nearest to void space, he draws fome conjectures relative to the uses and the end which comets may serve in the planetary system. His conjectures amount to this : that comets are real electrical bodies, designed to collect the electrical fluid, which has escaped from the planets ;--that these comets, heated by their approximation to the fun, communicate this fluid anew to the pianets, and thus the perpetual circulation of this active Auid, fo necessary to the great whole, is maintained and renewed inceflantly;-and that the operations of Nature in the planetary system, are carried on in a manner analagous to what we constantly observe and experience in the perpetual circulations of our atmosphere, where winds, vapours, and exhalations rise and float, then return to us in rain, snow, or fulminating explosions, and again are exhaled and raised anew. Every thing (fays our Author, and we are persuaded that he says the truth) is analogous and harmonical in universal 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 inspection of the plates.
A Memoir concerning the curves, described 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 same.
Memoir concerning the Natural History of the North-Sea * , and the fisheries carried on in it. By the Abbé Mann. In the first section of this ample Memoir, the laborious and learned Academician considers the limits of the North-sea, its form, its ancient and modern denominations, its situation with respect to other seas, and to the countries adjacent; its storis, their duration, velocity, force, and the natural causes of their direction; its climate, icy accumulations, depth, &c.
In the second section he treats of the tides and currents of the North-sea. Here, after confidering the laws of motion, that regulate the direction of fluids, he treats of the direction of
* By the North-sea, our Academician understands that part of the ocean which is comprehended between the eastern coasts of Great. Britain, from Dover to the islands of Shetland on the one side, and the opposite or weltern coalls of Norway, Denmark, and the New therlands as far as Calais, on the other,
the tides in general, and of those, more particularly, which come from the northern ocean * into the North sea, and by their direction from north-east to south-west, enter partly into that sea, and partly into the Atlantic, by the north of Scotland and Ireland. This direction our Author deduces from the folJowing principle, that the tides of the ocean, in consequence of the gravitation of its waters towards the moon, take naturally their
course from north-east to south-west in those parts of the ocean that are to the north of that planet, and from south-east to north west in those that are to the south. The application, of this principle to the course of the tides, and the irregularity and different directions of the coasts 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, sandbanks, &c. and open a field of discussion in which the learned Abbé expatiates, and in which we are forry that we cannot follow him. We are persuaded that .geographers and nav gators will read with fingular pleasure his principles, combinations, and conclusions, which seem to be the result of long observation and study. His theories are confirmed by the Marine charts and Atlaffes, both Dutch and English, which he appretiates with judgment in this section.
The third section relates to the sand banks and shoals of the North-sea, and the local changes that have been produced in it, by forms and other natural causes. The objects of discussion in this section are, the formation of sand-banks in the interior of the North-sea, and the reasons why they do not gradually increase in fize--the formation of banks near the coast-the effects and re-action of the banks already formed upon the tides and currents--the changes which the land-banks and the bottom of the North-sea undergo-the fand-banks in other feas, which differ in kind from those of the North-sea, and are owing to different causes.
The natural Productions of the North-Sea, its fisheries, and the methods of improving them, are the subjects of the fourth section ; which coinmences with a general account of the vegetable and anımal productions of the North-sea, and of the authors who have described them. This is followed by ample lists of its fith, shell-fish, aquatic birds, and plants. Our Author's account of the herrings, their different kinds, and their voyages, his particular remarks on the various sorts of fish contained in this sed, and immense gain which might be made by putting the fillieries on a proper footing, are curious and interesting.
* That is, from that part of the <cean which lies between the
'c pole and the coasts of Siberia, Nova Zembla, Lapland, and
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 especially on the Dutch and Flemish coasts, during these last 25 years ; a fact which is ascertained by the unanimous accounts of thofe employed in the fisheries. tributes this diminution to three causes, of which the two first are phyfical: the first is the sea's having lost a part of its fertility, and of the aliment which is necessary for fith. As in certain lands, the force of vegetation and the nutritive juices seem to fail and decline at certain intervals, the fea also may lose a part of that fertility which is peculiar to its bottom; and what seems to prove, says our Academician, that this is really the cafe, is the finall quantity of marine plants and productions, that is at present caft by the sea on the Flemish coasts, in com. parison with what there was about 18 years ago, and this quan. rity, as the Abbé Mann affirms from ocular observation, 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 small fish; as also that these latter contribute to the nourishment and subfiftence of the larger kinds, and that thus when any class of the finny tribe decays for want of food or shelter, the rest must be affected by this decay: not to mention, that the immense quantity of shrimps and other small filh that are taken and consumed on the coasts of Flanders, may also contribute to the diminue tion in question. A second cause of the diminution of the number of fish on the coasts of the Netherlands, is alledged modestly by our Author, not as ascertained, but as a matter of probable conjecture; it is the earthquake, that destroyed a great part of the city of Lisbon in 1755. This was felt all along the Flemish coast, where the agitation of the waters was so great as to drive the ships from their moorings. The line of direction that the shock of this earthquake followed in the Northfea, was the coast already mentioned; and it is natural to suppore (says our Abbé) that this shock may have been attended with sulphureous or bituminous eruptions, which may have left in the bottom of the sea fome pernicious or disagreeable quality, adapted to spoil or diminish the nourishment of the fish. But a more palpable circumstance that not only may, but must have contributed to the event complained of, is the manner of fishing that has been practised, these 25 years past, on the Flemish coafts, in oppoficion to the numerous edicts of tre sovereign. This manner our Academician describes in all its kinds, shews its pernicious consequences, and points out the meaiures that he thinks proper to prevent the growing evil.
This curious Memoir is the fifth that has been crmposed by the Abbé MANN, on the Natural History of the Netherlands,