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were bad, or that the observers were not expert, will answer no purpose. They were the inftruments and obfervers which M. Le Monnier's argument must rest on; and therefore let those of the French navigator have been ever so much better, which few will be hardy enough to affert, it will avail nothing to the point in difpute. Indeed it appears very extraordinary to us, how M. Le Monnier could fuppofe, that it was easier to commit an error of 7 or 8 degrees in the longitude, in so short a run, without difcovering it, on making land afterwards, than to mistake 3 in obferving the variation of the compass.

To thefe arguments it may be added, that although the Refolution was too much to the fouthward of the parallel of 54° when the croffed the Meridian of 3 Eaft of Greenwich, the longitude which M. Le Monnier has been pleased to affign for Cape Circumcifion, to fee it; yet her confort, the Adventure, was for feveral degrees on each fide of that meridian, full as near to the parallel of 54° S. as M. Bouvet was to the land when he first faw it. And on this day that the ship was exactly in that longitude, they had fine clear weather *. On the whole, we have no doubt but that M, Le Monnier's paper has been a hafty publication; and that when he has confidered the matter fully, he will find reafon to alter his opinion.7

MECHANICS.

CONTINUATION of the Inquiries concerning feveral Points in the mundane Syftem. By M. DE LA PLACE. Memoirs II. and III. In these two Memoirs, and the one mentioned in a preceding article, the Author propofes to determine the ofcillations of a fluid, which covers a fpheroid. The mechanical principles that are neceffary in order to find the equations of this problem, are known to the mathematicians, and M. De la Place makes ample and candid mention of the affiftance he has received from the learned refearches of the geometricians of the prefent century in the folution of thefe equations, with respect to several of the hypothefes that are confidered in this Memoir.

The learned Academician confiders this problem, with respect to the ebbing and flowing of the fea, the preceffion of the equinoxes, and the variations of the atmosphere, caufed by the attraction of the heavenly bodies. The phenomenon of the ebbing and flowing of the fea, of which Sir Ifaac Newton difcovered the true caufe (and concerning which we have the excellent treatifes of Mr. Maclaurin, and Meffrs. D. Bernoulli and Euler, published in 1740) has drawn the peculiar attention of

See the Account of M. Bouvet's Voyage, extracted from the archives of the French Eaft India Company, by M. D'Apres, and published by Mr. Dalrymple, F. R. S.

+ See Obfervations, p. 218.

many able mathematicians, during thefe laft forty years. But our Academician is the firft, known to us, who has confidered this phenomenon in all its extent, and with a view to all the caufes and incidents that are capable of affecting or altering it. He has carried ftill further than his predeceffors his inquiries into the influence of these different caufes, in order to be thus qualified for comparing the refults of his theory, with the notices that have been furnished by obfervation. He explains, by his theory, not only the phenomena which have been already explained, but likewise that of the almost entire equality of the tides of the fame day: it follows from this theory, that the difference between these two tides is in exact proportion to their force, and this is a fact afcertained by obfervation.

The depth of the water of the fea enters into this estimate: in order to correfpond with obfervations and phenomena, this depth muft be nearly uniform, and muft be, at least, four leagues, according to our Academician. The difcuffions relative to this object, are curious, interefting, and have in several places the merit of novelty. Equally curious are his observations on the denfity of the air, on the motion produced in the atmosphere by the attraction of the moon and the fun, which, according to the result of his analysis, must be imperceptible and infufficient to account for the permanent winds. In fhort, there is a rich and diverfified treasure of phyfical knowledge in thefe Memoirs, in which are feveral inftructive digreffions relative to the equilibrium of fpheroids, the law of powers at their furface, the figure of the earth, and the motion of the waves.

ART. III.

Memoire Phyfique et Medicinale montrant des Raports evidens entre les Phenomenes de la Baguette Divinatoire, &c. i. e. A Philofophical and Medical Reprefentation of the Marks of Refemblance that are obfervable in the Phenomena of the Virgula Divina, of Magnetifra and Electricity, together with Illustrations on other Matters of no lefs Moment, that are relative to this Subject. By M. T... (Thouvenel.) 12mo. Paris. 1781.

T

HE virgula divina, otherwife called baculus divinatorius, is (as moft people know) a forked branch in form of a Y, by the affiftance of which, many have pretended to discover mines and fprings under ground. This fingular phenomenon (like an object of a much higher, and more facred nature) has given occafion to the irrational extremes of enthusiasm and in-. credulity. Certain it is, that the philofopher has his prejudices as well as the fanatic: he is often tempted by vanity, to deny what he cannot explain; and not feldom rejects, as impoffible, facts, which he is furprized afterwards to fee confirmed by exAPP, REV. Vol. xlv. perience.

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perience. Nevertheless, we have here a philofopher, well known, and much esteemed in the learned world, who, by fix hundred experiments, made with all poffible attention and circumfpection, ascertains the facts attributed to the virgula divina, or divining rod, and undertakes to unfold their refemblance to the admirable and uniform phenomena of electricity and magnetism.

The first fection of his Differtation is defigned to fhew, that the facts are by no means impoffible. If no philosopher can deny that certain emanations proceed from the earth, it cannot be denied that thefe emanations may be most abundant in those places, where the earth's furface covers running or stagnant waters. Again; it cannot be pronounced impoffible, that thefe emanations should act powerfully on certain individuals, while they make little or no impreffion on the generality. The fenfitive powers vary greatly, not only in different claffes of animals, but even among thofe of the fame fpecies. So far there is no impoffibility in the cafe.-But granting, that emanations from fubterraneous waters may powerfully affect certain perfons, what connexion is there between this impreffion, and the motion or rotation of the hazel rod which is held in the perfon's hand, or laid over his fingers? This is a difficulty that deferved our Author's especial attention; though, after all, if the facts be ascertained, this difficulty only proves our ignorance. Nevertheless, M. THOUVENEL attempts the removal of it by a theory, which accounts tolerably well for this fingular phenomenon. He thinks, that the evaporations of fubterraneous waters have a course or current, perfectly fimilar to that of a fluid,-that they penetrate those bodies that are capable of receiving them,-that there are points of direction towards which they tend with a peculiar abundance, as happens in electrical experiments; and that, if thefe emanations direct their principal course to the extremities of the body, or to the hand, it is not abfolutely impoffible to conceive that they should communicate a motion of rotation to the divining rod-Our Author, indeed, obferves, that in the hands of Bléton, of whom we fhall presently fee the very fingular cafe, the rod is only a fecondary and fubordinate guide: for this man has an internal feeling, and an external motion which give the most certain notices of the prefence of water; and he only makes ufe of the rod to fhew it to others.-But let us proceed to facts.

Thefe we find in the fecond fection of this Differtation or Memoir, where the Author gives an ample account of his experiments, the trials to which he put Bleton, and the refult of his inquiries on this fingular fubject. He relates firft the general facts; afterwards the more particular ones which are adapted to lead to an explication of them, and points out their fimila

rity to the known phenomena of electricity and magnetism:We shall take fome fteps with him in this walk, though we. cannot help looking at him, now and then with a fufpicious eye.

Whenever Bléton is in a place where there are fubteranneous waters, he immediately feels a lively impreffion on the diaphragm, which he calls his commotion. This impreffion produces an oppreffion in the anterior and fuperior part of his breaft; at the fame time he feels a fhock, a general tremor, and chillness; his legs ftagger, the tendons of his wrifts. become ftiff, and grow convulfive; the pulfe is concentrated, and, gradually diminishes. All these fymptoms are more or less. ftrong, according to the volume and depth of the water; and they are more fenfibly felt, when Bléton goes against the fubterrane ous current, than when he follows its direction. When these emotions are violent, he is obliged to reft himself from time to time, and if he continues too long in this kind of exercife, his. body is weakened, he droops the whole day, feels a laffitude, and complains of a headach, accidents which generally follow strong nervous emotions.When he is placed not over the subterraneous current, but at the fide of it, all these symptoms cease almoft fuddenly; and there only remains an inward chillinefs, attended with a fmall oppreffion in the forepart of the breaft at a certain diftance from the water, he is abfolutely delivered from all these fenfations and emotions.

A very fingular circumftance attending the cafe of this man. is, that fubterraneous waters, which are ftagnant, produce no effect or impreffion upon him; nor is he affected by waters which are exposed to view, as those of rivers, lakes, &c. with this exception only, that when he has been in a boat, he complains, after fome time, of a head-ach, and a weariness through his whole body.-There is no remarkable visible difference between the phyfical conftitution of this man, and that of others, if we except this, that he is more fenfibly affected by change of weather, and variations in the ftate of the atmosphere, than other men. With respect to the peculiar impreffions that distinguish him from others, they are diverfified in their degree by certain. circumftances. A greater or fmaller quantity of electricity in the air renders them more or lefs lively. Dry and warm wea ther is the most favourable to his operations. His fenfations in his water experiments are much stronger before than after meals.. A fevere acute diforder had abfolutely deprived him of the faculty of perceiving water, and his fenfibility in this respect did not return, until three months after his recovery.

However furprizing the impreifion may be, which the proximity of fubterraneous waters makes upon Bléton, the pheno-. mena of his divining rod are still more wonderful. It is to be

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obferved,

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obferved, that this fingular man differs from his brethren of the profeffion, both in the ufe and choice of his rod; he does not grafp it closely; he does not warm it in his hands; he does not prefer a young hazel branch forked, newly plucked and full of fap. He places horizontally, on his forefinger and thumb, a rod of any kind of wood (except elder), fresh or dry, not forked, but only a little curved or bent. If the rod be ftraight, it does not turn upon its axis in the experiment, but only rifes fomewhat towards its extremities by little fprings: but if it is bent ever so little, it turns on its axis with more or lefs rapidity, according to the quantity of the water, and the force of its current. Our Author counted from thirty-five to eighty revolutions in a minute, and always perceived an exact proportion between the rotation of the rod, and the convulfive motions of Bléton.

This latter circumftance, at firft fight, rendered our Author diffident; and it may make the Reader fufpect, that Bléton had at command, both his own convulfions, and the motion of the rod. But M. Thouvenel's care in examining this matter, seems to remove all fufpicion of this kind. He placed himself, and feveral other perfons, fucceffively above the water fpring, with the rod placed, as Bléton placed it. The rod remained motionlefs, until Bliton approached the person that held it, and then it made upon the fingers of that perfon, the fame rotations that it had made on Bléton's. M. T. nevertheless remarks, that the rotations were more or lefs rapid and durable on ftrange hands, in proportion to the different conftitutions of those on whom the experiment was tried.The following circumftances are alfo very fingular:

The natural motion of the rod on Bléton's fingers, is a backward motion; but as foon as he withdraws from the fpring, in any line or direction whatever, the rod, which ceafes to turn the very inftant that he quits the fpring, undergoes, at a determinate diftance (which never varies), a motion of rotation in a direction contrary to its former one; but this new and forward motion does not go beyond one revolution. By measuring the diftance between the point where this retrograde motion takes place, and that from which Bléton fet out in withdrawing from the fpring, the depth of the fpring is generally found.

These facts are fo extraordinary, that, notwithstanding the extenfive knowledge of M. THOUVENEL, and his known probity and difinterefted nefs, they will naturally meet with unbelievers, among those who are not acquainted with the character and abilities of this intelligent and careful obferver. He himfelf feems to be well aware of this; and accordingly he tells us, to remove all fufpicion of impofture, miftake, or delufion, that thefe experiments have been repeated, in the space of

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