VII. While in your hofpitable fhell What wretched fate have I? The dog ftar's fickening funs I bear, In equal lots our human fortunes fall, We fee but what we want, not what we fear. There is, perhaps, hardly any fuch thing as a new moral; but the modification of fentiment is infinitely various, and the Reader who attends to thefe French fables, will not want, at leaft, that agreeable variety. ART. XIV. Sermons fur divers Textes de L'Ecriture Sainte, par J. H. Samuel Formey, M. D. S. E. Profeffeur de Philofophie, & Secretaire Perpetuel de L'Academie Royale de Prufje.-Sermons by M. Formey, Profeffor of Philofophy, &c. 2 Vols. 8vo. Leyden. 1772. THE fubjects of these fermons are not doctrinal and fpeculative points, or fuch as require a critical or elaborate difcuffion, but are all of a practical nature. The Preacher's manner is lively and animated, and his fermons, which abound with ftriking fentiments, are well calculated to make deep impreffions upon every ferious and attentive Reader.-The paffages of fcripture, from which he difcourfes, are these following: Prov. iii. 3, 4. 2 Corinth. vi. 2. Jer. xiii. 23. 1 Pet. ii. 21. St. Mark xvi. 15. St. Luke xii. 49., Phil. i. 12-14. Rom. ii. 4. Genef. v. 5. Prov. iii. 28. Jofh. xxiv. 15. 46-50. St. John xx. 11-16. Theff. ii. 10. Hebr. iv. 3. 2. Prov. x. 7. Prov. xxvii. 22. ART. XV. Hiftoires Diverfes D'Elien, traduites du Grec.-Elian's Various [or Mifcellaneus Hiftory, tranflated from the Greek, with Remarks. Svo. Paris. 1772. WE E have here a faithful, and, on the whole, an elegant tranflation of a Writer little known to the generality of readers, though, in the opinion of fome very good judges, he deferves to be ranked amongst the most agreeable writers of antiquity. The work may be compared to thofe mifcellanies fo well known under the name of ANA, and contains whatever appeared to the Author as interefting and curious in the productions 9 ductions of ancient writers ;-anecdotes, remarkable cuftoms, memorable fayings, fmart repartees, ftriking inftances of valour, magnanimity, love of country, &c. &c. Such collections, to borrow the Tranflator's words, are like a vast garden without any regular plan or defign, but where the want of regularity is amply compenfated by the abundance and variety of its productions; all of which, though not equally valuable, are either useful or agreeable. Ælian was born at Prænefte, a city of Italy, about the close of the second century; and, though he was never out of his own country, yet he wrote Greek, according to Philoftratus, with the fame elegance, as if he had been a native of Athens, and was firnamed Maywoos, on account of the sweetness of his ftyle. He taught rhetoric at Rome under Alexander Severus, on which account, probably, he had the title of Sophift. He was high priest, as Suidas informs us; from whence Perizonius infers, that he was nobly defcended, and in favour with the great men of thofe times.-His Hiftory of Animals is written with more ease and elegance than his Various Hiftory.—He is fometimes confounded with another writer of the fame name, who wrote upon Tactics, in the reign of Adrian, and was a Greek by birth. The Tranflator (M. Dacier of the Academy of Infcriptions and Belles Letters) has added fome very judicious and useful notes to his tranflation, which fhew him to be a man of learn. ing, and good tafte. AR T. XVI. Recherches fur les Modifications, &c.-An Enquiry into the various Modifications of the Atmosphere; containing a critical Hiftory of the Barometer and Thermometer; a Treatife on the Construction of these Inftruments, together with Experiments relative to their Ufes; principally with regard to the measuring of acceffible Heights, and the Correction of Refraction: Illustrated with Plates. By J. A. De Luc, Citizen of Geneva. 4to. 2 Vols, Geneva. 1772. Α AT the clofe of our laft Appendix we briefly announced the intended publication of this work. We have it now be fore us; but it has been fo fhort a time in our hands, that we have not yet been able to give it a complete perufal. We must therefore confine ourselves, for the present, to a brief view of the matters treated of in fome of the firft fheets of this ingenious and laborious performance. The Author begins his Enquiry by a philofophical hiftory of the barometer, from the days of Toricelli, the inventor, to the prefent time. In this hiftorical review we meet with the de1cription of fourteen different conftructions or propofed im 8 provements provements of this inftrument, accompanied with feveral judicious obfervations on their respective advantages and defects. It will be fufficient here curforily to enumerate, or briefly to characterize a few of them. The first alteration made in the fimple Toricellian tube, confifted in bending its lower extremity, and turning it upwards in the form of an inverted fyphon. By this fimple change it was rendered more eafily portable, and required a much smaller quantity of mercury. It follows however, from the very nature of this conftruction, as the tube is of the fame diameter throughout, that the extent of its scale is hereby diminished one half. It will perhaps appear ftrange to the Reader that, notwithstanding this and other inconveniences, the Author has preferred this conftruction to any other, in the courfe of his experiments: as he confiders the barometers thus formed, as the only ones which accurately indicate the real weight of the atmosphere, and accordingly correfpond invariably with each other. It would carry us too far even briefly to fpecify the caufes which, according to him, produce this precifion and uniformity in the barometers thus conftructed. At the fame time we should obferve that this minute accuracy is only, or, at least, principally, required in thofe delicate experiments where the barometer is used in the measuring of heights. The Author accordingly acknowledges that the inconveniences attending this conftruction render it not fo commodious, when employed as a fedentary barometer, or confulted only for daily obfervations of the weather. The unavoidable contraction of the fcale in the preceding barometer fuggefted the idea of adding a large ball, or refervoir, to the top of the fhorter tube, of fuch a capacity, that the level of the mercury contained in it fhould not be fenfibly altered by the rife or defcent of the mercury in the longer tube. This conftruction is ftill adopted by the common or itinerant preparers and venders of barometers. But it is liable to those ob. jections which induced the Author to prefer the fimple curve tube above-mentioned. In all the fubfequent attempts to improve the barometer, it has been the principal defign of philofophers to enlarge the extent of the scale, or to increase the fenfibility of the inftru ment. One of the first of these methods was fuggefted by Des Cartes; who did not however live to execute it. As the idea appears to us equally fimple and ingenious, and as we do not recollect our ever having met with a defcription of it in any of our fyftems of natural philofophy, we confider it as a novelty, and fhall endeavour to give fuch an account of it, as may perhaps convey a fufficiently clear idea of its conftruction, without the affiftance of a plate.. REV. App. Vol. xlviii. Rt It It confifts of a tube, about 27 inches long, which terminates upwards in a cylinder of a much larger diameter, to the upper extremity of which is connected a long tube of a very small bore. Suppofing the inftrument to be properly fitted up for a barometer, (the method of doing which the philofophical Reader may collect from what follows) its lower extremity, or that of the first mentioned tube, is to be confidered as immersed in a bafon of mercury; the whole of this tube being alfo full of this fluid, which likewife reaches up into the cylinder. The remainder of this cylinder is full of water, which extends up into the fmall tube. The top of this fmall tube is fealed, and the empty space above the water contained in it is, or at least ought to be, a perfect vacuum. It follows from the nature of this conftruction, that on a very small afcent of the mercury in the large cylinder, a proportional quantity of the fuper-incumbent water contained in it must be forced up into the narrow tube; where it will move over a space confiderably larger than that defcribed by the mercury, in the large cylinder. If we were to neglect the weight, or preffure, of the water, the quantity of its rife in the little tube would, in fact, be exactly determined by the proportion between its diameter and that of the cylinder; or, the motion of the water and of the mercury would be in the inverse ratio of the fquares of the diameters of the veffels containing them. It must be obferved, however, that the fmall column of water, thus raised into the narrow tube, gravitates, or presses on the mercury; and that, too, (according to a well known law of hydroftatics) not merely according to its quantity, but its beight. Suppofing then the whole range of the mercury in the fimple or common barometer, and confequently in the cylinder, to be two inches; and further fuppofing the fpecific gravity of the water to be to that of mercury as 1 to 14: if the difference between the diameters of the cylinder and tube be the greateft poffible, or, as the mathematicians fay, infinite; the entire fcale of variation in this inftrument will be 28 inches. In other words, the extent of its scale will be to that of the Toricellian or fimple barometer, In the inverfe ratio of the specific gravity of water to that of mercury. In practice therefore, the fcale will of course be somewhat less than 28 inches. M. Huygens conftructed a barometer of this kind; but found it fubject to an inconvenience which he could not remedy. The water contained in the cylinder and tube, on the removal of the preffure of the atmosphere, parted with its air, which rofe into the empty part of the tube, fpoiled the vacuum, and by its elafticity depreffed the water. Confidering the cafe as remedilefs, but unwilling to lose the advantage derived from this easy method of enlarging the fcale of the barometer, he conftructed, .on on fimilar principles, the double barometer, called after his name. Concerning this inftrument, as the defcription of it is to be met with in most of our fyftems of phyfics, we need only to obferve that, in it, the external air acts on the mercury by its preffure on the water or other light fluid, contained in a second open tube, connected at the bottom with the former, and rifing parallel to it. This conftruction, in which the water is expofed to the open air, is undoubtedly free from the inconvenience above-mentioned; but we do not agree with the Author (who neverthelefs, on the whole, condemns it) in thinking it preferable to the former; which is, in the first place, more fimple, and is free from one great and feemingly irremediable inconvenience that attends Huggens's inftrument; and which, we fuppofe, is the principal caufe why it is at prefent very seldom used. An evaporation, the precife quantity of which cannot be known, not only conftantly takes place from the fmall furface of the water in the open little tube; but from the much larger internal furface of the fame tube; alternately wetted, and deferted, by the water, during its frequent and extenfive motions upwards and downwards. As to the defect of Des Cartes's inftrument, we are far from thinking it incurable. The water employed in it may, for inftance, be previously deprived of its air as much as poffible, by boiling, and then fubjecting it to the air-pump. If, as may poffibly happen, fome air yet remains in the water, after the tube has been fealed, and efcapes from thence into the vacuum, it may eafily he expelled; firft by inclining the tube till the water rifes up to its extremity, then breaking the fealing, and immediately re-fealing the tube. To facilitate the operation, its upper extremity may be drawn out into a capillary ftem of fome length, which may at any time be eafily fealed, and the fealing, at any time, as eafily broke off. The operation, if neceffary, may be, at any diftance of time afterwards, eafily repeated; and when the liquor has been thus totally deprived of its air, the tube may be ftrongly fealed, in perpetuity. We can at prefent forefee only one circumftance that may poffibly affect the regularity of its motion. In hot weather, vapour may perhaps arife from the water in vacuo, capable of depreffing it by its elafticity. We do not imagine however that its effect would be confiderable. Poffibly too this inconvenience, if it were found to be of any material confequence, might be corrected by fubftituting fome light oily fluid, not eafily reducible into vapour, in the room of the water; by which means likewife the extent of the fcale would be enlarged. We have been tempted to beflow a little confideration on this invention of Des Cartes, on account of its fimplicity; and be Rr 2 caufe |