lines above-mentioned (viz. the distance of any point from the centre of force, and the perpendicular on the tangent), from an equation expreffing the relation between the abfciffa and ordinate of the curve; and the contrary, to find the relation between the latter, having the relation between the former expreffed in a given equation. The folution by Dr. Waring is extremely Jaborious and complex, and we have tried in vain to fimplify it. Its chief excellency confifts in its univerfality; for it applies to all curves. The relation between thefe lines in any particular curve may indeed be more eafily found by other methods; but then the operation must be different in different curves. The fourth propofition is, to find the forces F and F' tending to the centres S and S', when the velocity in any point, and the forces F", F", &c. to the given centres, S”, S′′, &c. are given. The fifth is to find the velocity in any point of a given curve when the forces F, F, F", &c. to the given centres S, S', S", &c. are given. The fixth is, to find Fin a given curve, when F' F", &c. are given. The feventh fhews how to find the curve described when the force to the centre, the velocity, and direction of the moving body, are given. The eighth relates to the forces in different parts of curves, compared with thofe of a falling body in different parts of a given line. The ninth and tenth refpect the refiftance of bodies moving in a medium. The remaining three propofitions are on the motions of bodies round moveable centres, and acted on by different forces in different directions. Here the reader will meet with investigations and demonftrations which require no fmall share of penetration in order to be understood.

Having fpecified the contents of the prefent Memoir, which hath taken up much of our time in the perufal, our Readers might expect that we should enter into an examination of each propofition: this, however, cannot be expected in a Review; the want of the figures, the few readers to whom it would afford entertainment, and above all, the difficulty of abridging what is already too concife, are all obftacles to fuch an attempt. We must therefore refer those of our Readers, who wish to entertain themselves with perufing this abftrufe paper, to the volume in which it is contained, informing them by the way, that they will fometimes meet with typographical errors that may occafion difficulties of confiderable magnitude. Page 96. line 4 from bottom, x+x+y) occurs for u

In many places the fluxional quantities want the point, which is of little confequence to adepts, but it may confound the novice, especially where the omiffion occurs twice in the fame expreffion, and in the fame line.

MEDICA L.

The Croonian Lecture on Mufcular Motion. By George Fordyce, M. D. F. R. S.

Mufcular motion having been fo often confidered, Dr. Fordyce begins his lecture with apologizing to his learned audience, if he fhould repeat what others have faid on the fubject before him, or fhould advance what might be deemed trite, or even puerile. He offers fome obfervations on motion in general, and on the inactivity of matter; and confiders motion either as communicated or origizal. If a body at reft, be impinged by a moving body, the impinging body will impart fome of its motion to the body at reft; and the motion thus imparted by an impulfe he calls communicated motion. We fhall use the Doctor's own words. If two fimple particles of matter, of any fpecies, not farther diftant from one another than the fun is from the earth, were both at perfect reft, these two particles would inftantly begin to move toward one another, if no other particle of matter whatever exifted. Motions produced in this way I call original motions.'.

Why the distance between the bodies is limited, we know not, nor do we apprehend the Author can juftify any limitation: If no other particle of matter whatever exifted,' and if the force of gravitation be, as ftated by Newton, reciprocally as the fquare of the diftance, the bodies would act on each other at any distance.

Dr. Fordyce proceeds: Many obfervations fhew, that mufeular motion is not a communicated, and therefore an original one. To fupport this affertion, much reasoning is adduced. As to the opinions of thofe phyfiologifts, who attributed muscular motion to fome agency of the nerves, our Author leaves them as mere chimeras of the brain,' p. 26.

The Doctor muft furely have made fome mistake in this bold declaration. Does not daily experience evince, that if a nerve be either cut through, or even compreffed, thofe mufcles to which it fends ramifications lofe all power of action?

Purfuing his reafoning a priori, he fays, in the fame page, It follows, that it is not neceffary for any motion or communication to pafs through any other matter, in order to bring the mufcular fibres into action."

Having, as he thinks, totally deftroyed all former hypotheses, Dr. Fordyce delivers his own. He fuppofes that all the original power exerted by any of the moving parts confifts in a power of particles coming nearer one another;' and as the power in two or more particles of matter, of coming nearer to one another, has been called by the general term attraction, the

peculiar

peculiar attraction which brings the parts of the muscles nearer to each other, he calls the attraction of life.' Of this attraction there are two fpecies, one that is conftant in the living animal, by which the particles are nearer to each other than in the dead animal, and which conftitutes the tone: the fecond is, when a moving part, for a short time, has its particles brought nearer one another than they are from their tone. If it continues only a few feconds, it is called action; but if for a longer time, it is called fpafm. He does not enlarge on tone and fpafm, but calls the attention of his audience to the confideration of that action, which is produced by applications to fome part of the body at a diftance from the moving part. He fupposes, that when any ftimulus or application whatever is made in any part, fuch application, without having any operation on the intermediate parts, gives a power of greater attraction to the particles of the moving part. He illuftrates this, by supposing that there is a machine moving by various powers, either original or communicated; and that in this machine are two magnets, which by their attractive power have come to a given distance from each other, but have been prevented from coming nearer by fome power endeavouring to draw them back: A much ftronger magnet applied to a part of the machine, in a certain manner, fo as not to touch either of the two already there, nor to affect any other part, may increase their power of attraction, fo as to make them overcome the refiftance, and come nearer to one another. By this illuftration, however, he fays that he does not mean to infinuate, in the smallest degree, that the powers of the body at all depend on, or have any thing to do with, magnetifm.' He then produces feveral inftances in which external applications produce motion in diftant parts of the living body; and, after a fhort hiftorical detail of the difcoveries in anatomy and phyfiology, he confiders the motions of the fluids in their refpective veffels. In this part of his difcourfe, he offers fome obfervations on topical bleeding. In certain cafes, a fmall quantity of blood, taken from the cuticular veffels in the affected fide of a pleuritic patient, has been found to cure the disease much more easily and fpeedily than a large quantity from the arm. The act of flowing out of the blood,' he says, from the veffels of the skin of the breaft, has an immediate action on the action of the moving parts of the pleura, and carries off the inflammation independent of the circulation or any of its laws.' We regret that the learned Lecturer has not defcribed the moving parts of the pleura, and in what manner an inflammation can be carried off, independent of the circulation.

that

He concludes his lecture with attempting to fhew, all the knowledge of the properties of the fluids, which has been acquired by modern and accurate experiments, hardly con

R 4

tributes

tributes any thing to the knowledge of applying medicines for the cure of diseases; and the ftudy of the laws of the attraction of life, or what has been called mufcular motion, is of confiderable importance.'

NATURAL HISTORY, &c.

An Account of a Mafs of Native Iron, found in South America. By Michael Rubin de Celis.

At Otumpa, a place in South America, in latitude 27° 28′ S. (long.?) a mafs of native iron, three yards long, and two yards and a half broad, was found in a bed of pure clay and afhes. The Author fuppofes it the production of a volcano.

Some Obfervations on the Heat of Wells and Springs in Jamaica; and on the Temperature of the Earth below the Surface in different Climates. By John Hunter, M. D.

.

Dr. Hunter, after making fome prefatory remarks on the temperature of the atmosphere, and of the earth's furface under 'particular circumftances, fays, For obtaining the temperature of the earth, the beft obfervations are probably to be collected from wells of a confiderable denth, and in which there is not much water; that is, we fuppofe, thermometrical observations, made in deep wells containing little water, are the best means of afcertaining the temperature of the earth. From what the Doctor advances in fupport of this opinion, it seems to be an accurate method of determining the temperature. The obfervations here recorded give the temperature of the earth in Jamaica, 80 degrees of Fahrenheit's thermometer, which is found to be allo the mean temperature of the atmosphere there.

Some Obfervations on the Irritability of Vegetables. By James Edward Smith, M. D. &c.

Here we have an account of fome experiments made on the Barberry, by which it appears, that the filaments of its flowers poffefs a confiderable degree of irritability. The fact was known before, but the particulars of it were never, to our knowlege at leaft, fo well or fo minutely defcribed as by the author of the prefent paper. In the natural ftate of the expanded flower, the Stamina lie on the petals, under the concave tips of which the Anthera fhelter themselves, and in this fituat on they remain perfectly rigid; but on touching the infide of the Filament near its bafe, with a fine bristle or blunt pointed needle, the Stamen inftantly incurvates itfelf, the Anthera embraces the Stigma, and heds its Pollen. A curious enquiry here prefents itself. Why is the infide of the bafe of the filament the only part which, being touched, produces the effect above defcribed? In what manner is the incurvation produced, or what change takes place in the internal structure of the filament, fo as to caufe it to alter its

14

sigid

rigid pofition, and remain afterward crooked? Attentive microfcopic obfervations may perhaps explain this phenomenon, which, if fatisfactorily known, may probably throw much light on vegetable phyfiology; a fubject hitherto little understood, although it has been much cultivated by fome of the greateft naturalifts of the laft and prefent century.

METEOROLOGY.

A Table of the mean Heat of every Month, for ten Years, in London. By William Heberden, M. D. &c.

This table extends from 1763 to 1772 inclufively; the obfervations were made 8 A. M. and 2 P. M.

A Meteorological Journal kept at the Apartments of the Royal Society.

The Journal, which is for 1787, contains feven columns. 1. The thermometer without; 2 W thin; 3. Barometer; 4. Rain; 5. Direction of the wind; 6. Force of wind; and, 7. The weather. An abstract of the whole is given at the end of the Journal. The greateft height of the thermometer without was 83, the least 27, and the mean of the whole year 51. Greatest height of the barometer 30.64, leaft 28.67, mean of the whole year 29.80. Depth of rain 16.971 inches.

No account is given of the electricity of the atmosphere, nor of the thunder, nor of the aurora borealis; the two laft phenomena were very remarkable in the course of last year.

The PHILOSOPHICAL PAPERS in a future Article.

ART. X. Difcourfes on Scripture Myfteries, preached at St. Mary's, Oxford, before the University, 1787, at the Lecture founded by the late Rev. John Bampton, M. A. Canon of Salisbury; with Notes Illuftrative and Critical. By William Hawkins, M. A. &c. 8vo. 5s. Boards. Rivingtons. 1787.

T may reasonably be queftioned, whether inftitutions efta

Iblimed for the express purpose of fanning the flames of theolo

gical controverfy, be equal proofs of the wifdom as of the zeal of their founders. The world nas for fo many ages experienced the mischievous effects of thefe difputes, and feen fo little reafon to expect that they will ever be brought to an amicable decifion, that, if it were not for the unfeasonable violence of a few zealots, we might hope to see the time, when all parties would agree to retire from the field of difputation, and meet on the common ground of general principles. But while annual premiums are given to champions on one fide, voluntary knightserrant will not be wanting, to accept the challenge, on the other,

The