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in dispute. Lenough to mer been everse and thereforers which
were bad, or that the observers were not expert, will answer no purpose. They were the instruments and observers which M. Le Monnier's argument must relt 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 dispute. 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 discovering it, on making land afterwards *, than to mistake 31° in observing the variation of the compass.
To there arguments it may be added, that although the Resolution was too much to the southward of the parallel of 540 when the crossed the Meridian of 31° East of Greenwich, the longitude which M. Le Monnier has been pleased to afsign for Cape Circumcifion, to see it; yet her confort, the Adventure, was for several degrees on each side of that meridian, full as near to the parallel of 540 S. as M. Bouvet was to the land when he first saw it. And on this day that the ship was exactly in that longitude, they had fine clear weather * On che whole, we have no doubt but that M, Le Monnier's paper has been a hasty publication ; and that when he has considered the macter fully, he will find reason to alter his opinion.7
MECHANICS CONTINUATION of the Inquiries concerning several Points in the mundane System. By M. De La Place. Memoirs II. and III. In these two Memoirs, and the one mentioned in a preceding article, the Author proposes to determine the oscillations of a Auid, which covers a Spheroid. The mechanical principles that are necessary 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 allilance he has received from the learned researches of the geometricians of the prefent century in the solution of these equations, with respect to several of the hypotheses that are considered in this Memoir.
The learned Academician considers this problem, with respect to che ebbing and flowing of the sea, the preceffion of the cquinoxes, and the variations of the atmosphere, caused by the attraction of the heavenly bodies. The phenomenon of the ebbing and flowing of the sea, of which Sir Isaac Newton difcovered the true cause (and concerning which we have the excellent treatifes of Mr. Maclaurin, and Messrs. D. Bernoulli and Euler, published in 1740) has drawn the peculiar attention of
Şee the Account of M. Bouvet's Voyage, extracted from the archives of the French East India Company, by M. D'Apres, and published by Mr. Dalrymple, F. R. S. it Sec Observations, p. 218.
many able mathematicians, during these laft forty years. But. our Academician is the first, known to us, who has considered this phenomenon in all its extent, and with a view to all the causes and incidents that are capable of affecting or altering it. He has carried ftill further than his predecessors his inquiries into the influence of these different causes, in order to be thus qualified for comparing the results of his theory, with the notices, that have been furnished by observation. He explains, by his theory, not only the phenomena which have been already exo, plained, but likewise that of the almost entire equality of the tides of the same 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 ascertained by observation.
The depth of the water of the sea enters into this estimate: in order to correspond with observacions and phenomena, this depth muft be nearly uniform, and must be, at least, four leagues, according to our Academician. The discussions relative to this object, are curious, interesting, and have in several places the merit of novelty. Equally curious are his observa-, tions on the density 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 insufficient to account for the permanent winds. In short, there is a rich and diversified treasure of physical knowledge in these Memoirs, in which are several instructive digressions relative to the equilibrium of spheroids, the law of powers at their sure face, the figure of the earth, and the motion of the waves.
A R T. III. Memoire Physique et Medicinale montrant des Raports evidens entre les Pbe
nomenes de la Baguette Divinatoire, &c. i. e. A Philosophical and Medical Representation of the Marks of Resemblance that are obfervable in the Phenomena of the Virgula Divina, of Magnetism and Electricity, together with Illustrations on other Matters of no Jefs Moment, that are relative to this Subject. By M. T... (Thouvenel.) 1200. Paris. 1781.
H E virgula divina, otherwise called baculus divinatorius, I is (as most people know) a forked branch in form of a Y, by the allistance of which, many have pretended to discover mines and springs under ground. This singular phenomenon (like an object of a much higher, and more sacred nature) has given occasion to the irrational extremes of enthusiasm and incredulity. Certain it is, that the philosopher has his prejudices as well as the fanatic: he is often tempted by vanity, to deny what he cannot explain; and not seldom rejects, as impoffible, facts, which he is surprized afterwards to see confirmed by exAPP, Rey. Vol. xlv.
perience. Nevertheless, we have here a philosopher, well known, and much esteemed in the learned world, who, by fix hundred experiments, made with all possible attention and circumspection, ascertains the facts attributed to the virgula divina, or divining rod, and undertakes to unfold their resemo blance to the admirable and uniform phenomena of electricity and Thågnetism.
The first section of his Differtation is designed to shew, 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 these emanations may be moft abundant in those places, where the earth's surface covers running or stagnant waters. Again; it cannot be pronounced impossible, that these emanacions Thould act powerfully on certain individuals, while they make little or no impreffion on the generality. The senfitive powers vary greatly, not only in different classes of animals, but even among those of the same species. So far there is no impossibility in the case. But granting, that emanations from fubterraneous waters may powerfully affect certain perfons, what connexion is there between this impresfion, and the motion or rotation of the hazel rod which is held in the person's hand, or laid over his fingers ? This is a difficulty that deserved 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 subterraneous waters have a course or current, perfectly similar 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 these emanations direct their principal course to the extremities of the body, or to the hand, it is not absolutely impoffible to conceive that they should communicate a motion of rotation to the divining rod.-Our Author, indeed, observes, that in the hands of Bléton, of whom we foall presently see the very singular case, the rod is only a secondary and subordinate guide : for this man has an internal feeling, and an external motion which give the most certain notices of the presence of water; and he only makes use of the rod to shew it to others. But let us proceed to facts.
These we find in the second feetion of this Dissertation or Memoir, where the Author gives an ample account of his experiments, the trials to which he put Bléton, and the result of his inquiries on this singular subject. 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 simila
sity to the known phenomena of electricity and magnetism: We shall take some steps with him in this walk, though we. cannot help looking at him, now and then with a suspicious eye.
Whenever Bléton is in a place where there are subteranneous waters, he immediately feels a lively impression on the diam, phragm, which he calls his commotion. This impression produces an oppression in the anterior and superior part of his breast; at the same cime he feels a shock, a general tremor, and chillness; his legs stagger, the tendons of his wrists become stiff, and grow convulsive; the pulse is concentrated, and, gradually diminithes. All these symptoms are more or less: Itrong, according to the volume and depth of the water; and they are more sensibly felt, when Bléton goes againft the subterraneous current, than when he follows its direction. When these emotions are violent, he is obliged to rest himself from time to time, and if he continues too long in this kind of exercise, his body is weakened, he droops the whole day, feels a lassitude, and complains of a headach, accidents which generally follow strong nervous emotions. When he is placed not over the subterraneous current, but at the side of it, all these symptoms cease almost suddenly; and there only remains an inward chilliness, attended with a small oppression in the forepart of the breast: at a certain distance from the water, he is absolutely delivered from all these sensations and emotions.
A very singular circumstance attending the case of this man, is, that subterraneous waters, which are ftagnant, produce no effect or impression upon him; nor is he affected by waters which are exposed to view, as those of rivers, lakes, &c. with this exa ception only, that when he has been in a boat, he complains, after some time, of a head-ach, and a weariness through his whole body. There is no remarkable visible difference between the physical constitution of this man, and that of others, if we except this, that he is more fenfibly affected by change of wea-, ther, and variations in the state of the atmosphere, than other men. With respect to the peculiar impressions that diftinguith him from others, they are diversified in their degree by certain. circumstances. A greater or smaller quantity of electricity in the air renders them more or less lively. Dry and warm weaa ther is the most favourable to his operations. His sensations in his water experiments are much stronger before than after meals., A severe acute disorder had absolutely deprived him of the facul. ty of perceiving water, and his fenability in this respect did not return, until three months after his recovery.
However surprizing the impresion may be, which the proximity of subterraneous waters makes upon Bléton, the pheno-, mena of his divining rod are ftill more wonderful. It is to be
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observed, that this singular man differs from his brethren of the profeffion, both in the use and choice of his rod; he does not grasp 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 litele curved or bent. If the rod be straight, it does not turn upon its axis in the experiment, but only rises somewhat towards its extremities by little springs : but if it is bent ever so little, it turns on its axis with more or less 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 convulsive motions of Bléton.
This latter circumstance, at first sight, rendered our Author diffident; and it may make the Reader suspect, that Bléton had at command, both his own convulsions, 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 several other persons, successively above the water spring, with the rod placed, as Bléton placed it. The rod remained motionless, until Bliton approached the person that held it, and then it made upon the fingers of that person, the fame rotations that it had made on Bléton's. M. T. nevertheless remarks, that the rotations were more or less rapid and durable on ftrange hands, in proportion to the different conftitutions of those on whom the experiment was tried. The following circumfances are also very singular:
The natural motion of the rod on Bléton's fingers, is a back. ward motion; but as soon as he withdraws from the spring, in any line or direction whatever, the rod, which ceases to turn the very inftant that he quits the spring, undergoes, at a determi. nate distance (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 distance between the point where this retrograde motion takes place, and that from which Bléton set out in withdrawing from the spring, the depth of the spring is generally found.
These facts are so extraordinary, that, notwithstanding the extensive knowledge of M. THOU VENEL, and his known probity and disintereftedness, 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 seems to be well aware of this; and accordingly he tells us, to remove all suspicion of impofture, mistake, or delusion, that these experiments have been repeated, in the space of