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The Theory of Jupiter and Saturn. By M. DE LA PLACE. By obfervations, it appears that the motions of Jupiter and Saturn have undergone confiderable variations, which could not be reconciled with the laws of gravity as delivered by NEWTON. The comparison of modern, with the ancient, obfervations, indicates an acceleration in the motion of Jupiter and a retardation in that of Saturn; while the obfervations of the moderns, compared with each other, offer a contrary refult; for M. LAMBERT has remarked that, fince the time of HEVELIUS to the prefent, Jupiter's motion has been retarded, while that of Saturn has been very fenfibly accelerated; and M. DE LA LANDE, from obfervations on Saturn's oppofitions, hath alfo concluded the mean motion of this planet to have increased within a century.. Hitherto, the causes of these variations have not been explained on the principles of univerfal attraction: M. DE DA PLACE, therefore, undertakes this laborious tafk; and he fhews that, fo far from being an exception to the general laws of gravity, this apparent irregularity is a neceffary confequence of thefe laws; and that it confirms the truth of the admirable principles of the Newtonian theory.
The memoir is divided into three fections; in the firft, M. DE LA PLACE gives an analytical theory of the periodical and fecular inequalities of the motions, of Jupiter and Saturn, arifing from their mutual action on each other. He has been parti-: cularly anxious to give to his refults the moft fimple forms; by, which means he has rendered them extremely convenient, and eafily applicable to the usual modes of calculation. What principally diftinguishes this from the preceding theories, is the. confideration of thofe inequalities which depend on the fquares and higher powers of the excentricities and inclinations of their orbits; former aftronomers, regarding only the first powers of these quantities in their inveftigations, have confequently left their results, which are at beft only approximations, much more imperfect than thofe of M. DE LA PLACE, who has included the 2d, 3d, and 4th powers.
Having in the firft fection determined the feveral inequalities, M. DE LA PLACE proceeds in the second to establish the theory of Saturn's orbit and motion. In order to apply the theorems. which he had deduced in the former fection, to either of the planets, it is abfolutely neceffary to know the value of the con- ! ftant quantities which make part of the algebraical expreffions already delivered; thefe are the mean distance from the fun, the mean longitude at a given epoch, the excentricity, the pofition of the aphelion and nodes, and the inclination of the orbit. The author remarks, that obfervations give only the true motions of the planets, and that, to determine the preceding elements, it is neceffary to have a previous knowlege of the perturbations
to which the planets are liable: the determination, therefore, of the inequalities, and of the elements of the planets, depend mutually on each other, and the only method of obtaining a knowlege of each is by a fucceffion of continual approximations, M. DE LA PLACE, therefore, uses the elements that former aftronomers have established, to approximate nearly the changes which the planetary motions undergo; and the elements, rectified by the confiderations of thefe changes, being again substituted in the algebraical expreffions, give the inequalities with great precifion. The epoch which M. DE LA PLACE has affumed, is the middle of the prefent century, viz. the beginning of the year 1750 and the corrected elements of Saturn at that time,
Mean longitude of the afcending node,
7° 21° 20′ 44′′ 8 28 13 9
3 21 31 17
Mean diftance from the fun,
2 30 20 0.056336 9.540073 12° 12′ 46′′.6
Mean fidereal motion in 365 days,
Having thus eftablished the elements, M. DE LA PLACE proceeds with rules for calculating Saturn's place at any given time, Rather than form new tables, he has adapted a correction for thofe of Halley, and fhews how it is to be applied; and in order to evince its truth, he has added a long lift of obferved places of Saturn, and compared them with the calculated places; the difference does not, in any cafe, amount to 2 feconds in longitude.
The agreement of ancient obfervations with M. DE LA PLACE's theory, ferves as a proof that the comets have no fenfible influence on our planetary fyftem. The irregularities of Saturn's motion have been fhewn to proceed from the action of Jupiter alone, and confequently that of the comets muft neceffarily be extremely little. May we not hence conclude that the comets are bodies whofe fpecific gravities are much less than thofe of our planets; and confequently that the motions of the comets will be much more affected by our planetary fyftem, than the motions of the planets are by the comets?
The great length of thefe investigations has obliged M. DE LA PLACE to referve the third fection of this memoir, which will contain the theory of Jupiter, for the fubfequent volume of the Hiftory of the Academy.
Experiments on the Smoking Oil of Vitriol from Saxony, and the volatile Concrete Salt obtained from it by Diftillation. By M. DE FOURCROY,
This fmoking oil of vitriol has been particularly mentioned by former chemifts, especially by MEYER and BERNHARD;
many of its properties, however, are not fufficiently described, nor the phenomena attending it properly explained.
This acid, which, from its confiftence, might be deemed extremely concrete, is only 5 gros *heavier than an ounce of water of the fame bulk; in contact with the air it continually emits a thick white vapour of a fulphureous finell, but in other refpects, perfectly resembles common oil of vitriol. Being put into a retort, to which a receiver was fixed, with the flightest degree of heat, a large quantity of thick white vapour paffed over, and a confiderable quantity efcaped from the juncture of the veffels, fmelling like the vapours of burnt fulphur: in a little time, and while the vapours were alfo paffing, a few drops of liquor came from the mouth of the retort, which arriving at the bottom of the receiver, formed themselves into a brown gelatinous mass; the vapours which were condensed on the fuperior and lateral parts of the receiver, formed white cryftals, refembling in fhape and texture the fal fedativus. The liquor which continued to come over, collected itself at the bottom of the receiver, and diffolved the gelatinous matter before mentioned. The vapour divided itself into two portions, the lighter, following the curve of the fuperior part of the receiver, was there condensed into a cryftalline mafs; and the heavier, falling on the liquor, was diffolved in it. Thefe appearances continued about two hours, when, fcarcely any vapours coming over, the receiver was changed, and the diftillation continued with an increased fire. After feven hours, the liquor in the retort became perfectly white, a dark coloured liquor having paffed into the receiver. Ten hours were confumed before the diftillation came ad ficcitatem; in the receiver were then found 71⁄2 ounces of ambercoloured oil of vitriol, whofe fpecific gravity was twice that of water; and the refiduum was about 6 grains of a white faline porous fubftance which had all the properties of calcined alum. The firft receiver, as foon as it was opened, was immediately, filled with a thick white fmoke, and it was with difficulty that the faline concretions formed in it, could be extracted. One ounce and 3 gros only could be collected; the quantity loft was estimated at 5 gros.
In a fecond diftillation, with an apparatus proper for obtaining the elastic fluid, there was the fame faline concretion in the receiver, and the quantity of permanently elaftic fluid produced from 2 pounds of the smoking oil, measured 6 French pints + The academician is rather deficient in his defcription of this fluid: he only fays, it appears to contain a little vital air, be
* A gros is a grain lighter than our apothecaries drachm, or 59 grains Troy.
A French pint is 58.1 English cubic inches, that is, 15, or nearly 1, of an inch greater than our wine quart.
caufe a candle burnt in it rather better than in the atmospheric air.'
The concrete falt is the next object of M. DE FOURCROY'S attention. From numerous experiments, he concludes that it owes its concrete ftate to fulphureous gas, fixed and diffolved in a concentrated vitriolic acid.
Water being mixed with the smoking oil of vitriol, and more efpecially with the concrete falt, difengages a confiderable quantity of fulphureous gas, with effervefcence; after which difengagement, the oil lofes its property of fmoking, or of yielding the concrete falt: hence he concludes the gas to be the cause of the particular phenomena which this acid prefents.
In our Review for December last, p. 497, we gave a short biftory of thefe capfula, under the name of Burfa Mucofa, and we should not now have refumed the fubject, had it not been for the fake of informing our anatomical readers, in addition to what we before faid, that a diftinct treatife on this fubject was published at Leipfic in 1753, by Profeffor JANCKE. M. DE FOURCROY gives an analyfis of this work, and fhews the imperfections under which it labours. The chief motive, which feems to have induced him to apply himself to the confideration of the mucous capfula, was the flight notice that has hitherto been taken of them by the generality of anatomifts.
In the first memoir, M. DE FOUR CROY explains the general Aructure of the capfula, defcribes their internal ftructure; and, by confidering their origin, fhews the effential differences between them and other membraneous productions, efpecially the cellular membrane and mufcular fheaths; and toward the end of the memoir he points out their uses.
Two Memoirs on the Tendons, and their Mucous Capfula. the fame.
The second memoir contains a fpecific defcription of all the mucous capfula, which M. DE FOUR CROY has difcovered, in his diffections, about the shoulder and the elbow. The defcription of the remaining capfule will be given in a fubfequent me
On the Structure of different metallic Crystals. By the Abbé HAUY.
In this curious memoir, the Abbé confiders the geometrical properties of the cryftals which he defcribes. There are more reafons for inveftigations of this kind than may generally be imagined the moft obvious one is, that cryftals are feldom found detached, or whole; and if, from the fize of the angle, the inclination of the fides, or some other circumstance (which may be determined by viewing only a part of the cryfta), we ean form a juft idea of the whole, this part of natural hiftory will be confiderably benefited.
The particular cryftals which the Abbé here confiders are, the cubical ferruginous pyrites; ferruginous pyrites with 12 pentagonal fides; the fame with 20 triangular fides; cubic iron ore; iron ore with rhomboidal fides; iron ore with 24 fides, of which 6 are pentagons and 18 are triangles.
Independently of the utility which may be derived, from this memoir, to the science of mineralogy, the fpeculative geometrician will find much amufement in the inveftigations of the properties of thefe folids.
We are, at all times, happy in having it in our power to perform the literary promises which we make to the Public; and are as much difappointed, as (we would modeftly truft) they are, when we are not able completely to fulfil them. With refpect to FOREIGN LITERATURE, various unavoidable incidents occur to make the latter cafe but too frequent. With much fatisfaction, therefore, we have thus completed our account of the last volume of the Parifian Memoirs; thereby prefenting to our readers many curious and useful particulars, with which, we hope, they will all be entertained, and fome, perhaps, inftructed.
Lettres Américaines, &c. i. e. Letters concerning America, by Count
Veil of myftery is thrown over this publication, which, like a fine lady's gauze handkerchief, feems calculated to tempt, rather than reprefs, curiofity. It is faid to be printed at Bofton; though the type and the paper are evidently French. It appears to have been tranflated from the Italian; but this we are left to guess; and the tranflator, who has not only added a preface and notes, but alfo confiderably enlarged the text, conceals his name, though he frequently refers the reader to his Notes on Don Ulloa's Memoirs, and to a Latin edition of Silius Italicus, which he fays he has published.
We do not fee any thing in the work, that can render this appearance of caution at all neceffary; except, that the Count diffents from the opinion of the church of Rome with refpect to chronology, and affigns to the deluge a much earlier period than. is generally allowed there are indeed a few mifrepresentations of paffages of Scripture hiftory, while the author profeffes the greateft regard for the facred writings; we are therefore inclined to confider them as rather the effect of ignorance, than of any defign to depreciate revelation. But most of these errors ale corrected by the annotations of the French tranflator, who feems to be better