on Dr. Priestley's difcovery, in which improvements, he himfelf had no inconfiderable fhare. We cannot quote this part of our author's work, because it A refers to plates, without which it I would not be well understood. We imagine, however, that most of our readers have seen the glafs apparatus commonly used for making thefe waters. It confifts of three parts. In the bottom veffel are put the ingredients for producing the fixed air. The middle one contains the water to be impregnated, and into which the air afcends through a perforated ftopple from the veffel beneath. The upper part is contrived to obviate the inconveniences that would otherwife attend the procefs, and conduct it to greater advantage. Chalk, limeftone, or marble, contain fixed air in very great quantity. Either of thefe being put into the bottom veffel, with a little water, and oil of vitriol, the vitriolic acid unites with the chalk, by means of what chemifts call elective attraction, and expels the fixed air. This air, paffing through the perforated ftoppie in the mouth of the veffel, is feen rifing in fmall bubbles through the water in the middle part, on the furface of which it remains; and by agitation, and even (though more flowly) without it, mixes with, or is diffolved by, the water, which thereby acquires the peculiar tafte and virtues of Pyrmont and other fimilar mineral waters. Dr. Nooth was the inventor of this apparatus; but it has fince been greatly improved by Mr. Parker and Mr. Magellan. The latter gentleman, by means of a double fet of the two upper veffels, and a wooden ftand, impregnated twice the quantity of water that can be done by the fingle machine in the fame time. The apparatus has been rendered more convenient, by adding a glafs cock to the middle vefiel, inítead of the fimple ftopple; and by forming both the middle and upper veffels of a conical fhape; by which means the water, by prefenting a greater furface to the fixed air, becomes more speedily impregnated. As the Pyrmont, and other acidulous waters, may be imitated by impregnating water with fixed air, fo may the fulphurcous waters of Aix-laChapelle, by impregnating water with fulphureous air. We owe this difcovery to the celebrated profeffor Bergman*, the Swedish chemift and philofopher, as we do other difcoveries refpecting mineral waters, which fhall prefently be noticed. The fulphureous air is produced by ufing Liver of Sulphur†, with the oil of vitriol and water, infiead of chalk or marble. This air being mixed with the water in the middle vessel, in the fame manner as hath been defcribed with regard to fixed air, gives it the ftrong ftinking fmell, and other properties, of the fulphureous waters. Befides thefe airs, however, there are other ingredients in mineral waters, by which thofe of the fame kind are diftinguished from each other, both in tafle and virtues. For example, Pyrmont and Seltzer waters are different from each other, though they are both impregnated with fixed air. This is owing chiefly to a quantity of iron diffolved by the fixed air contained in the former, whence it is alfo called a chalybeat water. And the latter contains a confiderable quantity of the foffil alkali, or fal fode. By chemical analyfis, the folid ingredients contained in any mineral waters may be difcovered; and by adding thefe ingredients to common water, and then impregnating the whole with fixed, or fulphureous air, or both, according to its nature, any mineral water may be perfectly imitated. In the natural water, there are ufually fome ingredients (as gyp、 fum, chalk, &c.) that are rather injurious to health, than neceffary to their virtue; and gives them befides a difagreeable tafte, whence Profeffor Bergman (to whom we owe the above im provements) very judiciously advises that thefe fhould be omitted. It * See a tranflation of this learned Profeffor's account of the Economy of the Universe, in p. 324. + Liver of Sulphur may be made by melting together equal parts of fulphur and pearl afhes into a red mafs. Or it may be bought of the chemists ready prepared. But, as Mr. Magellan fays, a mixture made over a gentle fire of three parts of clean filings of iron, with two of brimftone, is to be preferred, It appears, therefore, that mineral waters may not only be perfectly imitated, but may even be rendered more efficacious, wholefome, and agreeable, than the natural ones. We can not only make them ftronger of the folid ingredients, if occafion requires, but they may be made to imbibe double the quantity of fixed or fulphurecus air, that the natural waters are ever found to contain, as our author hath amply shown. Mr. Magellan then proceeds to give (from Bergman, &c.) the recipes for making the principal of thofe mineral waters; fpecifying the feveral ingredients, and their quantities, with proper directions for the proceffes. But as it would, perhaps, be unfair to tranfcribe them, we must refer the inquifitive reader to the work itfelf*. We fhall conclude this part of our account of Mr. Magellan's work with obferving, after Dr. Prieftley, that by means of thefe difcoveries, the trouble and expence of importing the foreign mineral waters may now be faved." The trouble, indeed, we have reafon to think, is fometimes faved; but the public is as yet very little benefited thereby, as the artificial waters arc, at least, in fome inftances, fold for the real ones, and at the fame price. It is probable, however, that if the artificial waters were fold as fuch, the public is not as yet fufficiently divefted of prejudice to give them the preference. Thefe prejudices, however, the work before us will tend to remove. We cannot withhold the concluding paragraph of this part of Mr. Magellan's ingenious pamphlet: "Pat this being a new branch of medical knowledge, which I am not qualified to urfue, I heartily wish, that fome young phyfician, endued with talents equal to the task, and actuated by a warm zeal for the benefit of mankind, fhould apply himself to this new branch of the medical profeffion; in which, no doubt, he will meet with all the encouragement he may have a right to expect, from the generofity and gratitude of the public." Mr. Magellan next enters on the fubject of Eudiometers, or inftruments for meafuring the goodnefs of refpirable air. Dr. Priestley discovered that if nitroust, and common or refpirable air, are mixed together, they will, after union, occupy lefs fpace than they did before; and that their contraction or diminution of bulk is greater as the common air is purer. Several contrivances have been propofed by philofophers, for meafuring this contraction; but none feem to answer better than the eudiometers invented by our ingenious author, and which are defcribed at length in the prefent pamphlet. We cannot, in a work of this nature, follow him in his defcriptions of thefe inftruments, for want of room; and because they continually refer to plates. In former editions of this pamphlet (for this is the third, though the work has not yet been noticed in any Review) Mr. Magellan defcribed three different eudiometers: but in the prefent, he has fuppreffed the account of one of them, as being too complex and coftly, "fimplicity in philofophical experiments (as the author juftly obferves) and cheapnefs of the inftruments required for their proceifes, being two of the most defirable circumftances in the investigation of natural phenomena." The firft of thefe inftruments confifts of a glafs, tube 12 or 15 inches long, and of an equal diameter. A glafs ftopple is fitted to the upper end; and a hollow glafs veffel, of a fomewhat globular form, to the lower, but by means of a neck, fo as to form a right angle with the tube. To this veffel two fmall and equal vials are fitted. The ftopple and vials being taken out, the eudiometer is to be filled with water, its lower part, or even the whole inftrument, being immerfed in the fame fluid. Close its mouth with the ftopple. Then fill one of the vials with nitrous air, the other with the air * A Treatife on Mineral Waters, both natural and artificial, has lately been published by Dr. Elliot; which alfo contains the recipes for making the artificial waters. + Nitrous air may be obtained by diffolving iron or copper in fpirit of nitre (aqua fortis.) The air flies of, and may be caught by means of a bladder, or other proper contrivance. The fpirit of altre should be diluted with almoft thrice its weight of water. air whofe purity is to be afcertained, and affix them to the inftrument. The ftopple may then be taken out again. The vials have hitherto been fuperior to the globular veffel of the Eudiometer. But that veffel being now turned, and the vials, of courfe, being beneath it, the airs which they contain, will, by the lefs fpecific gravity, rife above the water and remain in the upper part of the veffel, where they will mix. Their union may be expedited by gently agitating the veffel. This being done, the tube is to be accurately filled with water, and shut with the ftopple. And then being fufficiently inclined for ward, the air will quit the globular veffel, and rife to the top of the tube, driving downwards a proportionable quantity of water. Thefe deferiptions will, perhaps, be fufficient to give the reader a general idea of our author's eudiometers: but, for a more ample account of them, as well as for a number of particulars and circumftances neceflary to be obferved in making the experiments, we muft refer him to the work itself. The invention of eudiometers is a very important acquifition to natural philofophy. By means of these inftruments, we are enabled to measure the purity of the air (fo far at least as its phlogiftication is concerned) with almoft as great exactnefs as we measure its weight by the barometer, or its heat by the thermometer. Not to mention the great advantages which will be derived from them by the experiments in Natural Philofophy, we can (to use The pace which the two vials of the words of our author) by this means air would have occupied in the tube form a proper judgment concerning is known by means of a graduated thofe places where people may be able ruler, on which it is marked. And to live without danger of hurting their from the difference between that and conftitutions, by breathing, and being the fpace which the mixed airs now continually furrounded by noxious air; poffefs, the purity of the refpirable air which they have not yet been able to on which the trial was made is de- diftinguith from the moft wholesome, termined. except by a long and too late expe rience." Previous to building houfes, or any new fituation, recourfe will, in future, be had to the eudiometer, to difcover whether or not fuch fituation is healthful: and were this only advantage to be derived from these inftruments it would be great indeed! Our author's other eudiometer is ftill more fimple. It confifts of a straight glafs tube, of an uniform diameter, and about one or two feet long, ground air-tight, to the neck of a glass globe, about 3 inches in diameter, with a hole, and a glafs ttopple. A ftopple is alfo fitted to the other end of the tube, the mouth of which refembles a funnel. The inftrument being filled with water, and clofed at the globular end, is to be held in a vertical pofition, with the funnel part open, and under water. A vial of each kind of air is then to be thrown into it. Thefe rifing through the water in the tube, mix together in the globular part; and after the expanfion arifing from the heat generated by their mixture is over, the ftopple must be put into the mouth of the inftrument, which is then to be inverted. The ftopple of the globular part muft now be taken out, that part being under water; and the fpace which the air occupies in the tube mcafured, by means of a graduated ruler, as was defcribed before. On this occafion, the author very properly addreffes himself to Dr. Priestley, in the following ftrain: "The happy difcovery which you have made for the general benefit of mankind, and perhaps of almoft the whole animal creation of this globe, by finding that nitrous air is a true teft of the pu rity of refpirable air, which is abfolutely neceffary to life, and without which it is prefently extinct, gives a moft ftriking inftance of the blameable flownefs of mankind to pay a proper attention to thofe objects, the importance of which is infinitely fuperior to that of the numerous trilling novelties, which fo often fpread, with prodigious rapidity, through remote provinces, and even to the most distant countries of the earth." In that part of our author's work which treats of Eudiometers, he has examined, and very ably refuted feveral animadverfions of Mr. Cavallo, on his inftruments above defcribed. He infinuates, and feemingly with juftice, that Mr. Cavallo has been improperly influenced to eftablish the credit of Mr. Fontana's eudiometer, by depreciating his. He certainly appears to write with prejudice; and in his zeal againft our author, has fallen into blunders which one would imagine a man of his acknowledged abilities could hardly have been guilty of. He alfo appears to have acted difingenuously and uncandidly, as the following quotation will fhew: "There is fomething remarkable in what Mr. Cavallo fays (p. 327) viz. that I acknowledged to him, that I had defpaired of obtaining a conftant refult from thefe experiments with nitrous air. But, after my having acknowledged the fame uncertainty to all the world, in the very firft (page 26) and following editions of this letter; one may be apt to think, that Mr. Cavallo has overlooked it; and that he miftook what I had faid to him, as if it was a fecret or a friendly confidence, of which he had the generofity of availing himself, by difclofing it to the public, to expofe my poor eudiometers. If so, he was guilty of an unhappy overfight, indeed! 66 Now, if we combine with this probable fact, the peculiar advantage that Mr. Cavallo has endeavoured to draw from the unguarded experiments he came to fee in a friendly manner at my lodgings:--when it is confidered, that I was treating him with the most friendly regard, whilft he was muttering together fuch a heap of doughty arguments against my poor eudiometers: and that I have continued ever fince the fame behaviour towards him, whenever we met together, without his having uttered a fingle word of what he was doing, or ever afterwards making the leaft excufe for what he had done:-- I cannot help judging thefe circumstances deferve to be known, that the public may form a true eftimate of the whole." Mr. Magellan is certainly an ingenious, and what is more, an useful man: and, if we are rightly informed, his fimplicity of manners, and goodnefs of heart, are at leaft equal to his ingenuity. Such a man ought not to be wantonly perfecuted. * See Mr. Cavallo's Treatife on different Kinds of Air. ASTRONOM Y. ACCOUNT OF THE MEASURES TAKEN BY SOME PERSONS ABROAD, TO PERFECT THE THEORY OF THE MOTIONS OF THE GEORGIUM SIDUS. EXTRACTED FROM A LETTER OF M. DE LA LANDE TO THE AUTHORS OF THE JOURNAL DES SCAVANS, PRINTED AT PARIS. GENTLEMEN, N your Journal for February, 1782, you have given the elements of the circular orbit which I had calculated for the new planet which has been difcovered by Mr. HERSCHEL. That calculation was found to err 3' about the beginning of the prefent year; and the errors were fuch as fhewed that the planet had accelerated its motion. A bout that time M. DE LA PLACE, by an analytical method of his own invention, calculated the elements of its elliptic orbit. He makes the greater femi-axe 19.0818 femi-diameters of the earth's orbit; the half-excentricity, in feconds, 9815; the place of the aphelion, on the 21st of December, 1781, 11 23° 22' 58"; the true anomaly of the planet, at 18h 5' 40", mean time at Paris, 97° 29' 19, and its mean anomaly 102° 52' 7" M. boDE having remarked, in the ephemeris of Berlin for 1784, that the fiar, N. 964 of MAYER's catalogue, could not well be any thing elfe than the Georgium Sidus, as that itar cannot be now found in the place where MAYER obferved it, pains have been taken to examine the manufcripts of that celebrated aftronomer, which are pre ferved at Gottingen; and the date of the obfervation on which the pofition of that ftar was grounded, is September the 25th, 1756, at 10h 2118", mean time, at Paris; and gives its longitude, at that time, 11' 16° 37'43", and its latitude 48′ 23", This obfervation, at once fo complete and circumftantial, and found by a kind of accident which we could not even have hoped for, is near 25 years prior to that of Mr. HERSCHEL; and is found to accord very exactly with computations made from the elements of M. DE LA PLACE, recited above; and, therefore, we may look on the SIR, orbit of this new planet as already known to a very confiderable degree of exactness. From this obfervation of MAYER'S, we find, with great exactness, the pofition of the node for the year 1781, to be II 12° 47', and the inclination of the orbit, to the plane of the ecliptic, 46° 13 The greatest equation is 5° 27' 17", and is at 3° 3° 24′ 31′′ of the mean anomaly. At the time when MAYER obferved it, it was exceeding near its aphelion; and it is now not far from being at its mean distance from the fun. TO THE EDITOR OF THE LONDON MAGAZINE. Am happy to find your Magazine open to Mathematical Correfpondence. To fee a mifcellany amply fupported and fupplied with the daily improvements in that moft ufeful fcience has long been my moft ardent wifh, and I fhould efteem it a peculiar happiness if any communication of mine fhould be thought to merit a place in it, or tend to the advancement of science. I fubmit the following Obfervations on the late Lunar Eclipfe to your des termination, whether they are worthy infertion in your next. Sept. 19, 1783. W. G. OBSERVATIONS ON THE LUNAR ECLIPSE WHICH HAPPENED THE SEPT. 10, 1783. TAKEN IN TOWER-STEET. HE time-keeper was regulated to my own meridian by the mean of the tranfits of the two limbs of the fun on the fame day; allowing 3' 12" for the equation of time. Sept. 10, mean time. 9h 35m o" the moon had a cloudy appearance, especially on the N. E. limb. 9 38 O the cloudinefs much increased. 9 40 46 the eclipfe began on the limb between the two radi which pass through Grimaldus and Infula Ventorum. 47 48 53 54 56 10 7 cloudy. ditto. the convex of dark nefs approaching Infula Vextorum. cloudy. 33 Copernicus immerging. 20 ditto quite in the fhadow. 50 Infula in Maré Vaporum and Tycho both immerging. to II o Ijudged the moon to be half obfcured. 40 43 Mare Crifium of the convex of darkness from the northern horn, 30 approaching total darkness. o ditto. o ditto. o total dark. Sometime during the total darknefs the moon quite difappeared by the fogginefs of the air. LOND, MAG, Oct. 1783, |