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made and alleged to the contrary by Mr. Wilson, are inconclusive.'-Thele opinions and directions have the respectable fanction of Sir John Pringle, Dr. Watson, the Hon. H. Cavendish, Mr. Henly, Dr. Horsley, Mr. Lane, Lord Mahon, Mr. Nairne, and Dr. Priestley. Article 10. An Account of some electrical Experiments. By Mr.

William Swift, in a Letter to John Glen King, D. D. F.R.S.

There may be much ingenuity and contrivance in the plan and conduct of these experiments; but they are related in so obscure a manner, that we can collect nothing more from the most diligent perusal of them, than that the contriver and relator of them is not a Wilsonian, or Big-Endian. Though we, too, are Little-Endians, we can draw no consequences from the dark account which the Author has given of his experiments.

MATHEMATICAL PAPER S. Article

3. The Force of fired Gunpowder, and the initial Velocities of Cannon-balls, determined by Experiments, &c. By Mr. Charles Hutton, of the Military Academy at Woolwich.

This valuable paper contains an account of several fets of experiments made with a view to determine the actual velocities with which balls are impelled from given pieces of cannon, when fired with given charges of powder. The late ingenious Mr. Robins first discovered and practised the simple and excellent method, which was adopted by Mr. Hutton in this investigation, with material improvements. This method confifts in reducing the immense velocity with which a ball issues from a cannon, to a smaller velocity produced by causing it to strike against a heavy body, such as a large block of wood, swinging in the manner of a pendulum. The ball being lodged in the block, the two bodies proceed together, after the shock, with a velocity which bears the same ratio to the original velocity of the ball alone, that the weight of the ball has to that of the ball and block united. This velocity, thus reduced from 1000 to perhaps 2 or 3 feet, is easily measured by observing the magnitude of the arch, or rather the chord of the arch, described by the pendulum; and this is ascertained by fixing a graduated tape or ribbon to ihe bottom of the pendulum; which, by the motion of the latter, is drawn through a little machine which gives it a moderate degree of friction.

Mr. Robins made his experiments with only musket balls of about an ounce weight, and an apparatus of a proportional size. The present were made with cannon balls, from one to near three pounds weight, and an appropriate apparatus. They appear to have been executed with great care and accuracy; and their results lead to conclufions of considerable importance, both to the theorist and the practical artillerist.

Article

Article 16. On the Arithmetic of imposible quantities. By the

Rev. John Playfair, A. M. In this paper the Author explains the grounds of those obscurities and paradoxes, from which Geometry is free, but which have been introduced into Algebra; particularly with respect to the doctrine of negative quantities and its consequences. He obferves that, in geometry, every magnitude is represented by one of the same kind; lines are represented by a line, and angles by an angle: whereas, in algebra, every magnitude is depoted by an artificial symbol, to which it has no resemblance; and the magnitude itself is liable sometimes to be neglected, while the symbol becomes the sole object of attention, after the connection between them no longer exists. Accordingly, the conclusions of the analyst, which hold true only with respect to the symbols, being transferred to the quantities themselves, obscurity and paradox necessarily ensue. The Author exemplifies there obfervations by considering the nature of imaginary expressions, and the different uses to which they have been applied. Article 17. Reflections on the Communication of Motion by Impact

and Gravity. By the Rev. Isaac Milner. M. A. &c. The Author of this paper endeavours to point out, and distinguish, what is real from what is verbal, in the long agitated question concerning the vires vivæ, or the forces of bodies in motion; from a serious persuasion that the laws by which motion is communicated are still very materially mistaken by sensible persons; ' - and that the right understanding of these laws is of the last importance in practice :' as the good or bad fuccess of some very expensive projects has depended upon it. His design in this paper is to discriminate between the real and the merely verbal part of this ancient controversy; and to point out to the controvertists the grounds of their mutual mistakes and misapprehensions; which he exemplifies in several in{tances. Article 18. Observations on the Limits of Algebraical Equations ;

and a general Demonstration of Des Cartes's Rule for finding their Number of Affirmative and Negative Roots. By the same.

MISCELLANEOUS PAPERS. Article 2. Of the Heat, &c. of Animals and Vegetables. By

Mr. John Hunter, F.R.S. We shall not, for many reasons, attempt to give any abstract of the numerous experiments related in this paper. They are indeed too complicated to admit of abridgment: and with respect to those relating to the Author's trials on living animals,-the unfortunate dormice, in particular, who were the subjects of his calorific and frigoric tortures, --We respect the sensibility of our Readers, and our own, too ftrongly, even to dwell a moment on the subject. We have repeatedly, and, we hope, not quite

unavailingly, unavailingly, born our testimony against the studied cruelties of phyfiologists; particularly in our 420 Vol. March 1770, page 197; our 5ift Vol. September 1774, page 229; and our 55th Vol. August 1776, page 120; to which we refer our Readers, and particularly the Author. Such of his experiments as are not liable to this objection we recommend to the Reader's perusal; though we think great uncertainty must attend the thermometrical observations made on such large bodies as trees.

There is some power, or, we should rather perhaps say, some circumstances in the economy of living vegetables, by which their juices are so far protected from the action of very intense cold, as not to be frozen by it; though the same juices, when they are no longer contained in their proper canals, will be frozen in the temperature of 31 or 32 degrees. The juices of the spruce fir, juniper, &c. are not affected, in countries where the thermometer falls many degrees below o; and where the feet and noses of the inhabitants are frequently frozen. When the tree however is killed, in consequence of an extraordinary increase of cold, its sap or juices freeze; and by their expansion, in the state of ice, split the tree, with a great noise, into a considerable number of pieces. The numerous experiments which the Author has made on this subject, and here relates, have not yet enabled him to solve this difficulty. Article 8. An improved Method of Tanning Leather. By David

Macbride, M. D. The great advantages which the most useful and necessary arts may derive from the lights furnished by the experimental Phikosopher, and particularly the Chemist, are well exemplified in the paper before us. Their progress would be still more rapid, did the philosopher poffess the practical knowledge of the artist; or if the two characters were united in the same person:-a combination which seldom happens.

The Author was led to the discovery of this improved method of tanning leather, in consequence of the experiments which he formerly made on the dissolvent power of calcareous earths deprived of their fixed air, or quicklime (erroneously printed quicksilver at page 119 of this article), which were published in his Experimental Esays. One of the Author's principal improvements consists in using lime water, instead of plain common water, in which the bark is to be steeped, in the preparation of the ooze. This menftruum, he observes, lo completely exhausts the bark, and makes it go so much farther than when plain water is used, that a pretty strong ooze may be prepared from the tan, or spent bark, which the tanners now consider as completely exhausted, merely by infusing it afresh in lime water.

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Another advantage is gained, in the Author's method, by the employing oil of vitriol largely diluted with water, instead of the fouring, as it is called, which the Tanners have hitherto, with great trouble and uncertainty, procured from fermented rye or other grain; not knowing that a mere acid was all that was wanted in the process. This useful fubftitution has already been universally adopted by another class of artists, the bleachers of linen; who, however, were not without difficulty prevailed upon to quit their old routine, in preparing a fouring likewise from rye or barley, or sour butter-milk; through an ill founded apprehension that the vitriolic acid would injure their cloth.

The improvements described in this paper are not founded solely on the conjectures of a speculative Chernist. After some trials made on small pieces of raw leather, the method was prosecuted in a large common tan-yard ; and its efficacy has been fully proved by the experience of near ten years, during which ti the Author thought proper to keep it secret. He here bestows his discovery on the public, in a paper of instructions drawn up in terms sufficiently clear, to enable any intelligent Tanner to avail himself of the improvements described in it. Article 10. 'An Account of the Isand of Sumatra, &c. By Mr.

Charles Miller. Among the particulars here related concerning this island, we meet with an account of the Battas, a people who live in the interior parts of it, called the Cafia country; and who differ from all the other inhabitants in language, manners, and customs. They eat the prisoners whom they take in war, and hang up their skulls as trophies in their houses. Man's Aesh, we are told however, is eaten by them in terrorem, and not as their common food; though they prefer it to all others, and speak with peculiar raptures of the roles of the feet and palms of the hands. They expressed much surprise on being informed that white people did not kill, much less eat, their prisoners.'

From this country the greatest part of the Cassia that is sent to Europe is procured. The Author (son of the late Botanic Gardener) failed in his attempts to discover the cinnamon tree. The camphire trees abound in this country, and constitute the common timber in use. In these trees the camphire is found native, in a concrete form. It is remarkable that, in this state, it is sold to the Chinese, at the price of 250l. or 300 l. per cwt. but these dexterous artists contrive to furnish us Europeans with it at about a quarter of that price. Article 20. An Essay on Pyrornetry and Areometry, and on Phyfical Measures in general. By John Andrew ďe Luc, F. R. S.

This long article contains many ingenious observations, principles, and facts, relative to the construction of various phi

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losophical losophical instruments, adapted to measure either the relative or the real dilatation of bodies by heat, the specific gravities of liquors, &c. accompanied with a plate representing a Pyrometer and Areometer of the Author's contrivance.

The paper is translated from the French : the original text however is, very properly, subjoined at the bottom of each page. Even this laft is not to be read hastily; but we are forry to observe that the most unwearied attention, joined to an intimate knowledge of the subject, will scarce enable the mere English reader even to guess at the Author's meaning, in many parts of this servile and un-idiomatical translation. The trantlator religiously gives us word for word, and almost invariably follows the French construction. To the obscurities hence arifing he adds others, by mistaking even the grammatical construction of that language.--To give only an instance : Les loix que suivent les differens effects, he translates, the laws that follow different effects :' whereas, in the original, the different effects are said to follow the laws.-A similar passage is translated in the very same manner.-In short, M. de Luc's translator feems to be a cousin-german to Rousseau's in the following Article.

The remaining articles, on which we shall not particularly dwell, are, Art. I. in which Sir William Hamilton gives an Account of certain Traces of Volcano's on the Banks of the Rhine.--Art. 4. A new and fingular Case in Squinting, well described by Erasmus Darwin, M. D. F. R. S.-Art. 6. An Account of a large Stone near Cape-Town, by Mr. Anderson. - Art. 7. On Mr. Debraw's Improvements in the Culture of Bees, by Nath. Polhill, Esq.-Art. 14. An Account of the Earthquake at Manchester, September 14, 1777, by Mr. Thomas Henry, F. R. S.- Art. 19. A Journal of a Voyage to the East Indies, in the Year 1775, by Alexander Dalrymple, Esq. F. R. S.—and Art. 12. 21, 22, 23, 24, and 25. Containing Meteorological Journals of the Weather, kept at Fort St. George in the East Indies, by Mr. Wm. Roxburgh; at Lyndon, by Thomas Barker, Esq., at Montreal, by Mr. Barr; at Hawkhíll near Edinburgh, by John M'Gouan; at Bristol, by Samuel Farr, M. D.; and at the House of the Royal Society. From the last we learn that the variation of the needle, in July 1777, taken from a mean of several observations, was 22°, 12'.

ART.

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