party fpirit, and is a feasonable warning not to enter into any dangerous or vigorous measures against the conduct of our prefent governors, without exacting a political creed from leaders, who, under the fpecious pretence of public zeal, are to all appearance only planning fchemes of private emolument and private ambition. ART. X. Aftronomical Obfervations, made in the new Obfervatory at Cambridge, in the year 1767 and 1768, with an Account of feveral Aftronomical Inftruments. By the Rev. Mr. Ludlam. 4to. 10 s. 6d. Boards. Cadell. 1769. A Midft the many unpleafing profpects, which thefe unhappy times present to a Briton, it is a fatisfaction to find, that true fcience ftill lifts her head, flourishing, unhurt, amidst the general decline of our principles and manners, and promifing to fecure to us fome of those laurels which a long feries of illuftrious ancestors have tranfmitted to us. In the nobleft parts of fcience, natural and moral philofophy, the reputation of the prefent age is little inferiour to that of any which have preceded it; not even in aftronomy, where the fame of a Newton may feem to eclipfe all other merit; for we ftill may promife ourselves the most important and useful improvements, while, aided by geometry, we continue to tread in the fure paths of experiment and obfervation. This laudable fpirit of philofophizing is happily promoted by that affiftance which, wealth can beftow, in the erecting obfervatories, furnishing them with their expenfive apparatus, and liberally providing for the maintenance of thofe who fhall be chofen to conduct the obfervations. The prefent publication is (if we are not mistaken) the firft-fruits of the obfervatory at Cambridge. The name of the Author is fufficient to recommend the work to thofe who are converfant with the philofophical world, nor will their expectations be dif appointed in the perufal. The first part is a regular and well difpofed ferics of aftronomical obfervations from the 9th of July, 1767, to the 5th of Auguft, 1768; to thefe are added fome obfervations (taken by Hadley's quadrant) of the distance of the moon from the fun or ftars, in order to try the utility of a method of determining the longitude, recommended by Dr. Halley, revived by Mr. Maikelyne, and now patronized by government. Thefe obfervations are followed by remarks upon them, which are introduced by a defcription of the inftruments, and the manner of ufing them; in which the clearness, precifion, and minutencís of the Author is greatly to be praifed. Though his publication has nothing which is not valuable, this perhaps will be found to be of not the leaft utility;, as it is but feldom that philofophers Cc 4 will will condefcend to explain to the world the inftruments by which themselves are so much affifted, or give any detail of the application of them; and in the few, who may be thus condescending, it is very rarely that we meet with those talents which are neceffary to execute this public fervice in an intelligible and fatisfactory manner. The Author proceeds to give fome of the ufes which may be made of the obfervations in afcertaining the latitude of the place, and the obliquity of the ecliptic. But it is to be obferved that there does not appear to be that correfpondence in the refults, which might be expected from the accuracy of meridian obfervations, taken in a proper and well furnished obfervatory, and conducted by fo excellent a philofopher and mechanic as Mr. Ludlam. This will appear from the following summary in P. 57. Latitude of Cambridge. Mean of 1 latitudes deduced from observations near the folitices Latitude from the obfervation of the polar star Mean of the latitudes from D° of circumpolar flars Mean of 26 latitudes 52 12 53 52 12 384 52 12 25 4 52 12 24 5 52 12 40 I 52 12 36 3 Here the greatest difference from the mean of 26 latitudes is 17 feconds, the difference between the leaft and greateft of the above latitudes is nearly 30 feconds, and the difference between the leaft and greatest of the 26 latitudes is I min. 13 fec. If therefore the mean of feveral obfervations be subject to a probable error of 17 feconds, and two fingle oblervations differ from each other by so much as 1 min. 13 fec. and this with all th advantages which an obfervatory fuppofes; what can be expected from a single obfervation at fea? And how much may thofe be deceived who promife themfelves fo much from the prefent lunar method of determining a fhip's longitude! But the following article in the remarks on the obfervations, adds greatly to this fufpicion. Mr. Ludlam has annexed the longitude of Cambridge according to twelve different computations of Mr. Lyons from the obferved distances of the moon from the fun and ftars in the preceding collection, as taken by Hadley's quadrant. Thefe diftances are not the refult of a fingle obfervation, but the means of 3, 5, 6, 7, 8, 9 obfervations; and yet the greatest difference of the longitudes determined by them from the mean of the 12 longitudes is no lefs than 54 42", and the difference between the leaft and greatest is 1° 28'. Mr. Ludlam allows that diftances may probably not be taken fo exactly at fea as thefe were, and that the computation of the time cannot be fo near the truth as that fhewn by a fixed regulator, regulator, yet concludes that the utility of the method may be inferred from thefe trials. But furely the very contrary is the juft inference. If with the advantage of obferving at land, aided by Mr. Ludlam's excellently contrived ftand, and that' great defideratum, the determination of the time from a fixed regulator, fo great an error is incurred as 54′ 42′′, what utility is to be expected from the application of this method at fea? Where, not to mention the other difadvantages, the time alone, especially in nocturnal obfervations (which will neceffarily occur the most frequently) is fubject to fuch uncertainty, as is enough to overfet the whole operation, and deftroy all confidence in it. There is at prefent no method of determining the time at fea, not even in the day, and much lefs at night, which can form any bafis for the difcovery of the fhip's longitude by whatever method. If thereto be added all the other probabilities of error, it is to be feared, it is perhaps to be demonftrated, that the medium error by the lunar method at fea is much nearer to two degrees than one. The remainder of the volume is a very valuable prefent to the public, containing many new, ingenious, and ufeful obfervations and theorems in aftronomy, and mechanics as fubfervient to the uses of aftronomy. The ftand for placing an Hadley's quadrant in the plane of a great circle paffing through the centre of the moon and ftar, is a piece of elegant machinery, and the defcription of it does the Author almoft equal honour with the conftruction, Next follow the defcriptions of a tranfit telescope of tin, of a wooden pendulum, and of telescopes with feveral eye glaffes. The theorems for the rectifying of fome aftronomical obfervations, the improvement of pendulums and clockwork, arc all of the most useful tendency, and fhew the Author's great knowledge both in the geometric and analytic art. His account of the properties of Hadley's quadrant, though new and ingenious, is not, in our opinion, fo eafy and obvious as what we have formerly feen given to the public on the fame fubject. The last of Mr. Ludlam's papers is one given into the Board of Longitude on the fubject of Mr. Harrifon's time piece, containing a fhort view of the improvements made or attempted by it, and Mr. Ludlam's judgement of the machine; which is given with great candour and generofity. Though Mr. Ludlam does not decide pofitively on the merits of Mr. Harrifon's watch, but rather inclines to doubt its utility for the purpose intended, yet the public will probably infer, from that degree of perfection to which Mr. Harrifon confeffedly attained, and the teftimony which Mr. Ludlam fo often bears to the fingular abilities of this wonderful mechanic, that his attempts towards the folution of that difficult problem, the longitude, have been too coldly received, and perhaps too haftily dropped in favour of a` method 3 method which a little experience will probably difcover to be impracticable. The public will not expect that we fhould make any extracts from the various articles which compofe this ufeful publication; but we will venture to recommend it as a valuable addition to the philofophical knowledge of this kingdom. ART. XI. Philofophical Tranfactions, Vol. LVIII. for the Year 1768, continued: See the Review for March, p. 191 ANTIQUITIES. HIS clafs wholly confifts of five papers written by the Rev. John Swinton, B. D. F. R. S. &c. which contain defcriptions of fome inedited Punic and Etrufcan coins, accompanied with interpretrations of the infcriptions, and obfervations upon them. In the 31ft article, Mr. Swinton attempts the interpretation of a infcription on a Punic coin, which he fuppofes to have been ftruck in the ifle of Gozo, and which has never hitherto been explained. In the 37th is contained an elucidation of an Etrufcan coin of Paflum, in Lucania, emitted from the mint there, about the time of the focial war. The 38th article contains fome remarks upon a denarius of the Veturian family, with an Etrufcan infcription on the reverse, never before published. In the 39th Mr. S. gives a defcription of a Punic coin belonging to the ifle of Goza, hitherto attributed to that of Malta: and in the 40th, he gives us fome obfervations on an inedited coin, adorned' with two Punic characters, which may, as he apprehends, be fafely pronounced Aleph and Koph, and must be confidered as forming the first part of the name of fome noted city, either in Sicily or Africa.' Mr. S. very fagaciously retreats into a corner of this very spacious field of conjecture; and not being able to prevail with himself to attribute this coin to any town in Africa,' he fixes upon the celebrated city of Agrigentum in Sicily, the moft antient part of which was denominated Axea or Acra; in which place he fuppofes it to have been ftruck. The Author has fhewn great learning and ingenuity in fupport of his lections of the infcriptions on thefe different coins: but the Reader must be poffeffed of a tafte perfectly congenial to his own, and be endued with no inconfiderable portion of true antiquarian gravity and irrifibility, whofe features will not unbend a little on obferving the air of importance, and folemnity of diction, with which he treats the difcovery of a hitherto unobferved form of a Punic character; the bringing to light the true name of an Italian general, which had been moft miferably mif-fpelt for many ages; or the complete reftoration of a crippled Samnite clement, deprived, by the ruthlefs tooth of time, of alt its, members except its tail. MATHEMATICS and MECHANICS. Article 3. An Effay on the Force of Percuffion, by William Richardfon, M. D. communicated by William Heberden, M. D. F. R. S. The Author of this Effay endeavours to throw fome light on the celebrated question, whether the force of percuffion be in proportion to the mafs multiplied into the fimple velocity, or into the fquare of the velocity. Few mathematical questions, we shall obferve, have been more copiously or strongly agitated than this; each fide of which has been moft tenaciously and acutely maintained by mathematicians of the greatest name, for near a century paft. In fupport of the mathematical reasonings. and metaphyfical principles employed in this difpute, experiment has been appealed to by the controvertists on both fides: but experiment has feemed to give its decifion alternately in favour of each of the parties. The queftion has by others, with great propriety, been confidered as, in great measure, a mere difpute about words; and nothing, it has been faid, was wanting to reconcile the difputants, but to define their terms, and particularly to agree in affixing a precife meaning to the word, force; for it is certain that the partifans of both doctrines, notwithstanding their difference of opinion on this question, would all give the fame folution to a mechanical problem propofed to them. The intention of the Author of this paper is, to inquire whence the diverfity of appearances, and the different effects produced in the experiments made with a view of determining this queftion, have proceeded; and particularly in thofe where the force of percuffion has been deduced from the impreffions made in foft bodies. He fufpected that the various refults of thefe experiments might arife from the nature of cohesion; and that while the force of percuffion produced an effect on the whole mafs of matter which receives the flroke, in proportion to the velocity of the impinging body, it might, at the fame time, in feparating the cobering parts from each other, produce an effect in proportion to the fquare of the velocity.' He was led into this way of thinking by obferving that a chord, which would bear a very strong pul, might easily be broken by giving it a fudden jerk; as alfo that the weight of a hammer did not contribute fo much in driving a nail, as the quickness of the motion given it by the driver.' He accordingly conftructed an apparatus, in order to afcertain the truth or fallity of this fuppofition; determining first to make experiments on fach foft bodies (clay, for inftance) as have a confiderable degree of cohefion; and then to try the fame body either dried, or converted into brick, and reduced into powder, and by thefe means, in a great meafure, deprived of that quality. From the |