quaintance with the Greek language, is very clearly evinced by this collation of the manufcript Scholia on Euripides, and more particularly by the judgement with which he had adopted and approved the best lections.” We mut not, however, omit informing our readers that the name of Thryliitius occurs very frequently in the Mifcellanea Obfervationes, which were begun by Jortin, in England, and continued for feveral years after he had given up the fcheme, by the learned Philip D'Orville, and Peter Burman, the elder*, in Holland; and that wherever it is mentioned, he is mentioned with the praife which he merited. Valckenaer then proceeds thus: "I have been informed by the celebrated Reifke, that under the capital letters is concealed the name of George Frederic Thryllitius, who was born near Leipfic, in the year 1688. After he had publifhed feveral fpecimens of his learning, and was preparing for the prefs the Пpoon, Opping, and Meloμmpma, of Tzetzes, he died at Wittenberg, in 1715. The wonderful depth of erudition which Thryllitius had acquired, and his intimate ac* How far Burman was concerned in the management or expence of this work, we know not; but it is certain, that many of the notes in the earlier voluines, befides feveral of the original pieces, are his. EDITOR. MATHEMATICS. O. E. ANSWERS TO MATHEMATICAL QUESTIONS. CONSTRUCTION. RAW any line DB at pleasure, which DRA Ratin extreme and mean proportion at A, fuch that BA×BD DA2, make AE perpendicular to and equal AB; through E draw DEC, to meet BC drawn parallel to EA in C, and the triangle ACB fhall be fimilar to the required one. DEMONSTRATION. E By fimilar triangles DA : AE (AB) :: D DB: BC, and, by conftruction, DA: AB : DB: DA, where ex equo, DB: DB :: DA: BC. Therefore, BC=DA, but AB=AE by contruction; therefore the triangle AED triangle ACB. 65. QUESTION (II. July) anfwered by Mr. G. SANDERSON. CONSTRUCTION. Make AD equal to the given fum of the fides and perpendicular, on which take AB equal to I the given bafe, and bifect it in O; erect the indefinite perpendicular BK, and on O, as a center, at the diftance AD defcribe the circle DHI, cutting BK in H: then by Prob. 19, Simplon's Geometry, make KH fuch that FK × HK÷2HBAO, BO; from K to the circle DHI apply KG=AO, draw AG cutting BH in E; laitly draw CO perpendicular to AB, and meeting AG in C, join CB, and ACB is the triangle required. DEMONSTRATION. Defcribe the circle about the triangle ACB; alfo conceive the circle DHI to be completed, and HB produced to meet it in b. Then, becaufe KB is perpendicular to AD, therefore Bb HB, Euc. TII. 3. and becaufe HK×HK+HB (HK×Kb) A K H G E B =AG2 (A02) by conftruction, KGE is a right angle, Euc. 37, and 18, III. Whence the triangles KGE, ABE, AOC, and BOC are equiangular, but KG= AO=OB. · EG=CO, and KE=AC=BC=AE, therefore AC + CB-+-CO =AE+EG=AD, the given sum. Now, because the arc ACB is bifected in C, it is well known that the perpendicular CO and the fum of the fides AC+CB (=AE) is the greatest that can be drawn in the fegment ACB; confequently, if either be greater, the vertex Cust fall without the circle, but two lines drawn from A and B to meet without the circle contain an angle lefs than ACB, the angle in the fegment; therefore, ACB is a maximum. Q. E. D. 67. QUESTION (I. Aug.) anfwered by TASSO, the propofer, by Mr. Emerson's method of Increments. Cor. The fum of the given feries, infinitely continued is 3.n+1.n+2.ntz II 18 68. QUESTION (II. Aug.) anfwered by the propofer, Mr. J. WALSON, when the vertical angle is a right angle. ABC BE FBG, by Euc. VI. 8 cor. Hence, BC: BG:: FB: AB, by VI. 17. and GC: BG::FA or BG: AB, by divifion. Now, GC: GK or BG::GK: GH, by VI. 8. cor. therefore, GH=AB. SCHOLIUM. Q. E. D. AB must be less than BC. For when AB BC, BG becomes equal to GC and the triangle vanifhes. GKC is ifofceles when BC is equal to twice AB together with the diagonal of the fquare, whofe fide is AB. When BC is greater, GK and GH will be the leffer fide and fegment, and vice versa. MATHEMATICAL MATHEMATICAL QUESTIONS. 80. QUESTION I. by A. M. It is required to explain and demonftrate the principle on which a top, whilf it is whirling and having its axis inclined to the horizon, recovers its perpendicular pofition. **Emerfon, in his Treatife on Centripetal Forces, has endeavoured to explain this principle, but has failed. 81. QUESTION II. by ASTRONOMICUS. To determine the fituation of the planet Mercury in refpect to the earth, when the intenfity of its light to a fpectator on the earth is the greatest. 82. QUESTION III. by Mr. J. WALSON. Let there be two circles given in pofition and magnitude, and let two right lines be drawn, each of which touches both circles; if the points of contact in one of the circles be joined, and the line joining them be produced until it meets the line which joins the two points of contact in the other circle, the fegments of these two lines, intercepted between the point where they meet each other and the points of contact, will be proportional: a demonftration of this is required. The anfwers to thefe queftions may be directed (poft-paid) to Mr. Baldwin, in Paternofter-row, London. ASTRONOM Y. THE FOR THE LONDON MAGAZINE. HE following remarks on the planet Mercury, as they have never appeared in any of our publications, will probably be acceptable to many perfons, at leaft certainly they will be very much fo to thofe who make aftronomical obfervations, as their object is to point out in what part of that planet's orbit it appears the moft bright, and particularly when it can be feen with meridian inftruments. Ancient obfervations of Mercury are very fearce; Ptolemy, in his Almageft, has only fixteen, two of which are erroneous: after thefe, until Tycho's time, I find none that have been of any ufe, except a few made by Gualtere, towards the end of the fifteenth century. Copernicus complains that he never could get a good obfervation. Tycho-Brahe, Longomontanus, Margraff, and Riccioli were more fuccefsful, and made feveral, but moft of them are of little ufe for correcting the tables, as the planet then was not in the requifite part of its orbit; this objection is alfo made to many of the numerous obfervations of Hevelius, though perhaps fome of them might be acceptable, if reduced with fufficient exactnefs. Halley and La Hire obferved with more precifion, as did alfo our great aftronomer Flamstead; but this lait hardly ever noticed Mercury, which is very unaccountable, as it is the only object in the heavens he has neglected. Of all the above-mentioned aftronomers, I believe none of them, except La Hire, ever faw Mercury on the meridian; they obferved the planet when near the horizon, which obfervations are well known to be far less accurate; and even La Hire fucceeded but very feldom, for in the Memoires de l'Academie Royale des Sciences, of 1764, the Abbé Chappe d'Auteroche fays that only eight or nine meridian obfervations are to be met with in the preceding Memoires; but fince that year many have been made, as may be feen in the different publications of M. M. Le Gentil, de Thury, de la Lande, Mafkelyne, Meffier, &c. though at at the fame time moft of them mention the extreme weakness of the planet's light, and how frequently they were difappointed, which was owing to their looking for it when fartheft from the fun, in which fituation Mercury always appears very faint. We are now come to the principal object of this paper, which is to point out in what part of his orbit Mercury is invifible, when apparently the moft bright, and alfo when he begins to lofe and recover his light. Monfieur D'Arquier, in the preface to his Obfervations Aftronomiques, mentions that Mercury is invifible towards his inferior conjunction, and vifible near the fuperior; and this I have been informed is nearly all he fays on the fubject; I fhall, therefore, refer to a memoir I heard read at the French Academy of Science, containing obfervations made in 1778 and 1779, by Mr. Edward Pigott, and which they ordered to be printed in their Savans Etrange: from that paper moit of the following articles are felected, but are given here with alterations; as fince that was written I have alfo made fome additional obfervations and remarks, which, to avoid repetition, I take the liberty to blend with thofe made by Mr. Edward Pigott. ift. Mercury is brightest between his elongations and fuperior conjunction, very near to which laft he generally can be feen: he becomes invifible foon after he has paffed his elongation going towards his inferior conjunction, and becomes vifible again a few days before his next elongation. This is the refult of above fixty obfervations made with a tranfit inftrument, the telescope of which is a three feet achromatic, magnifying fifty times. It must be always underftood, that all these remarks allude to the appearance the planet affumes when on the meridian. 2dly. When Mercury has a great fouthern declination, or when the atmosphere is in the leaft thick, he feldom can be feen in thofe parts of his orbit where he begins to recover his light, or is much diminished in brightnefs. 3dly. The apparent brightness of Mercury, when brighteft, is about the fame as that of Sirius when in conjunction with the fun. 4thly. As an additional proof of its brightnefs, I find eight obfervations, made with an eighteen-inch quadrant, the telescope of which is two feet focal length, the aperture of the glaffes one inch, magnifying eighteen times; with which inftrument it is very difficult to fee ftars of the feventh magnitude when the wires are in the leaft illuminated. 5thly. The quick alteration of the planet's brightnefs is particularly remarkable, being fometimes very confiderable in lefs than twenty-four hours. 6thly. On the 11th of July, 1779, Mr. Edward Pigott obferved the planet, which was then lefs than three degrees diftant from the fun; we may, therefore, conclude, that fometimes it can be feen even in conjunction with the fun. 7thly. It is fingular that Mercury and Venus appear brighteft in the oppofite parts of their orbits; the firft between his elongations and fuperior conjunction, the other between her elongations and inferior conjunction; therefore, Venus is feen as a crefcent in great perfection, particularly in her inferior conjunction, while Mercury is feldom feen on the meridian in fuch perfect phafes. 8thly. In confequence of the rule fettled by the first article, it is easily known how often Mercury may be feen in a year. I find that during the next it can be obferved on the meridian about 200 times. I hope, by thus having fhewn with what facility and how frequently Mercury can be feen on the meridian, even with the most common inftruments, that the practical aftronomer may be induced to pay more attention to this much-neglected planet. Nothing more remains, but to add that the historical part of this paper is chiefly extracted from the Memoires de l'Academie des Sciences, and that we are indebted to the diftinguished Monf. de la Lande for the greateft part, as alfo for the correctnefs of the prefent tables of Mercury, which feldom err more than a few seconds. B ALGOL MEDICIN E. TO THE EDITOR OF THE LONDON MAGAZINE. SIR, Send you fome account of the difcovery, the introduction, and the explosion of transfufion of the blood, together with a few reflections upon this fubject; which I have been led to draw up, from obferving that a propofal has been made for the revival of this practice, in a pamphlet lately publithed, entitled, "Some new Hints relative to the recovery of Perfons drowned, and app hently dead." As the histories of the experiments which have been made upon this fubject are cifutively fcattered through the different volumes of the tranfactions of our own and foreign focieties, I have perfuaded myfelf that it would not be difpleating to your readers to fee them thus brought to their view in an abridged and collected itate. I am, Sir, your's, &c. ON TRANSFUSION OF BLOOD. [T was about the year 1666 that transfufion P. The relation of this experiment was followed I was firit tried in England and France. For by a paper, written by the fame hand, contain ing full and particular directions relative to the manner in which transfufion thould be performed. It is therein advifed that the blood of the recipient animal be fuffered to flow out in proportion as that of the emittent aaimal runs in: that had been given before by Libavius. This laft author does not make any mention of letting the blood of the animal that is to receive flow out, either previously to or during the performance of the transtufion; and he alfo fays that the blood is to pafs from the artery of the animal that is to emit into the artery, not the vein, of that which is to receive. the priority of the 'difcovery both nations for a long time contended: now, however, it is pretty apparent that the English were the first who practifed transfufion upon brute, and that the French were the first who made trial of it upon men. But, according to an Italian philofopher, thus, at the end of the operation, all, or at least who published a book at Rome, about this time, the greater part of the blood which remains in entitled "Relatione dell'Effoienze fatte in the vellels of the former, may not be its own Inghilterra, Francia, ed Italia intorno la Tranf- blood, but the blood of the latter. It is allo fufione del fangue," it fhould feem that tranf- directed, that one of the quil's (for it did not at fufion is not of fo modern a date as that of 1666, that time occur to Dr. Lower that metalline tubes but that it was known at least, if not practifed, would anfwer better) be inferted into an artery fifty years farther back. In proof of this, the of the emittent animal, and another into one of Italian author quotes the following paffage from the veins of the recipicnt animal. Thefe diLibavius's Defon, fynagmatis avcanum chi-rections, it will be feen, differ from thofe which micorum, printed at Francfort, in 1615: “ Adfit juvenis robujtus, fanus, far guiné fpiritufo plenus. Adfii exiargfus virias, tenuis, madianas, vix animam trabens, Mag for arshaboat tui dis avgertes, inter fe congruentes, eperiat arteriam rebrifti, & tubulam ir gerai minatque; max et grati arteriam findet, & tubutum fåmineum infigat; jam aus tubulus fibi mutus applicit, & ex juno fanguis arterialis, calcus & piviturfus faliet in ægrotum, vraque vitæ fontem afferet omnemque languorem plet; i. e. Let there be a tout healthy young fellow, full of blood and ipirits; and a weakened, thin, meagre perfon, that has hardly any lite w.thin him. Let one fkilled in the butinets be provided with fome ilver tubes, properly adapted to each other; let him make an incition into the artery of the robuft perion, and having introduced a tabe into it, let him fecure it therein; next, let him open one of the fick man's arteries, and nx in it a tube fitted for being introduced into the other tube; let him now falten the two tubes together and the warm and fpirituous arterial blood will then be propelled from the healthy into the tick perfon; and tgether with this blood the fountain of life will be carried, and all languor will be in an inftant removed." Dr. Lower, it should appear, was the first who published an account (a the Philofophical Tranfactions for 1606) of the experiment of transfufion from one dog into another. He took a mastiff and a cur, and into the latter introduced the blood of the former. The confequence was, that the maid died, and that the cur, when he was untied, ran and fhook h mitit, as if he had been only thrown into water. In the following year, 1667, many fuccef.ful transfufions were made. Amongst others, that which was made upon a bitch feems to be a very remarkable one. She loft, during the operation, nearly thirty ounces of blood, and received, as it was fuppofed, about the fame quantity from the other animal. The bitch not only furvived this operation, but, what is hardly credible, underwent very foon afterwards even a more dangerous one; for her fpleen was taken out, the perions who did it not obferving the precaution of tying up the veilels from which this vifcus was feparated. Since that time the bitch became with puppy, and littered, and continued afterwards to be well. This experiment, it is obferved, thews that large transfufions are not dangerous. The fame year Sir Edm. King published an account of an experiment of transfution from a calf into a sheep, by the veins only. Previous to the operation, 49 ounces of blood were taken from the fheep. The transfufion was then made, and when it was thought that as much blood had in this manner been given to, as had been taken away from the sheep, the operation was stopped, When the sheep was untied, it feemed to be as vigorous as it had been before the lofs of its own blood. This animal was afterwards purpofcly bied to death. |