Valentinian, Roman Emperor. I hare omitted, you observe, St. James Major, one of the Apostles, so called to distinguish him from St. James the Less; also Olaus Magnus, Johannes Magnus, and Albertus Magnus, have no place assigned them in the list; neither have I noted the expressions, the Great Mogul, the Grand Signior, the Grand Chan, and the Grand Lama of Tartary; as these do not so much denote the pre-eminence of particular persons, as the grandeur of their several states and empires. I am, Sir, yours, &c. 1771, March T. Row. XLIV. Description of a wonderful Automaton. In a Letter from the Rev. Mr. Dutens. SIR, Presburg, (in Hungary,) Jan. 24. I LEAVE others to describe to you the magnificent feasts and rejoicings occasioned bere by the presence of the Empress Queen, the Emperor, and all the imperial family. It is in my opinion almost impossible to do justice to that affability and condescension, so full at once of regard and confidence, with which these great personages converse with their subjects; and no less so to describe that noble tribute of love and reverence which they receive from their subjects in return. I shall content myself to inform the public, through the channel of your correspondence, of an invention which reflects no less honour on the sciences, than on the city of Presburgh which hath produced it. During my stay in this city, I have been so happy as to VOL. III. сс form an acquaintance with M. de Kempett, an Aulic Couns sellor and Director-General of the salt mines in Hungary. It seems impossible to attain to a more perfect knowledge of mechanics, than this gentleman hath done. At least no artist has yet been able to produce a machine, so wonderful in its kind, as what he constructed about a year ago. M. de Kempett, excited by the accounts he received of the ex. traordinary performances of the celebrated M. de Vaucanson, and of some other men of genius in France and Eng. land, at first aimed at nothing more, than to imitate those artists. But he has done more, he has excelled them. He has constructed an Automaton, which can play at chess with the most skilful players. This machine represents a man of the natural size, dressed like a Turk, sitting before the table which holds the chess-board. This table (which is about three feet and a half long, and about two feet and a half broad) is supported by four feet that roll on castors, in order the more easily to change its situation ; which the inventor fails not to do from time to time, in order to take away all suspicion of any communication. Both the table and the figure are full of wheels, springs, and leavers. M. de Kempett makes no difficulty of shewing the inside of the machine, especially when he finds any one suspects a boy to be in it. I have examined with attention all the parts both of the table and figure, and I am well assured inere is not the least ground for such an imputation. I have played a game at chess with the Automaton myself. I have particularly remarked, with great astonishment, the precision with which it made the various and complicated movements of the arm, with which it plays. It raises the arm, it 'advances it towards that part of the chess-board, on which the piece stands, which ought to be moved; and then by a movement of the wrist, it brings the hand down upon the piece, opens the hand, closes it upon the piece in order to grasp it, lifts it up, and places it upon the square it is to be removed to ; this done, it lays its arm down upon a cushion which is placed on the chess-board. If it ought to take one of its adversary's pieces, then by one entire movement, it removes that piece quite off the chess-board, and by a series of such movements as I have been describing, it returns to take up its own piece, and place it in the square, which the other had lefi vacant. I attempted to practise a small déception, by giving the Queen the move of a Knight; but my mechanic opponent was not to be so imposed on; he took up my Queen and replaced ber in the square she had been removed from All this is done with the same readiHess that a common player shews at this game, and I have often engaged with persons, who played neither so expeditiously, nor so skilfully as this Automaton, who yet would have been extremely affronted, if one had compared them to him. You will perhaps expect me to propose some con jectures, as to the means employed to direct this machine in its movements. I wish I could form any that were reasonable and well-founded ; but notwithstanding the minute attention, with which I have repeatedly observed it, I. have not been able in the least degree to form any hypothesis which could satisfy myself. The English ambassador, Prince Guistiniani, and several English Lords, for whom the inventor had the complaisance to make the figure play, stood round the table while I played the game. They all had their eyes on M. de Kempett, who stood by the table, or sometimes removed five or six feet from it, yet not one of them could discover the least motion in him, that could influence the Automaton. They who had seen the effects produced by the loadstone in the curious exhibitions on the Boulevards at Paris, cried out, that the loadstone must have been the means here employed to direct the arm. But, besides that there are many objections to this supposition, M. de Kempett, with whom I have had long conversations since on this subject, offers to let any one bring as close as be pleases to the table the strongest and bestarmed magnet that can be found, or any weight of iron whatever, without the least fear that the movements of his machine will be affected or disturbed by it. He also withdraws to any distance you please, and lets the figure play four or five moves successively without approaching it. It is unnecessary to remark, that the marvellous in this Automaton consists chiefly in this, that it has not (as in others, the most celebrated machines of this sort) one determined series of movements, but that it always moves in consequence of the manner in which its opponent moves; which produces an amazing multitude of different combinations in its movements. M. de Kempett winds up from time to time the springs of the arm of this Automaton, in order to renew its MOVING FORCE, but this, you will observe, has no relation to its GUIDING FORCE or power of direction, which makes the great merit of this machine. In general I am of opinion that the contriver infuences the direction of almost every stroke played by the Automaton, although as I have said, I have sometimes seen him leave it to itself for many moves together; which, in my opinion, is the most difficult circumstance of all to comprehend in what regards this machine. M. de Kempett has the more merit in this invention, as he complains that his designs have not always been seconded by workmen so skilful as was requisite to the exact precision of a work of this nature; and he hopes he shall, ere long, produce to the world performances still more surprising than this. Indeed one may expect every thing from his knowledge and skill, which are exceedingly enhanced by his uncommon modesty. Never did genius triumph with less ostentation. I am, Sir, yours, &c. &c. 1771, Jan. XLV. Method of taking impressions from Medals. MR. URBAN, CHIEFLY owing to the cost required for purchasing a ca. binet of medals, it has happened, that the study of them has hitherto been confined, comparatively, to a few individuals. Another principal impediment to the cultivation of an acquaintance with them has arisen from the difficulty of understanding the inscriptions thereon, for want of a sufficient knowledge of languages; on which account in particular, this study has been condemned by the illiterate as barren and useless; but such as are acquainted with the advantages which have already resulted from these nummi memoriales, cannot hesitate a moment to assist the promotion of a more general pursuit of the subject. While colossian statues, and the hardest marbles, with their deepest inscriptions are destroyed by accident or by time, and paintings finished with the highest colours quickly fade, a medal shall survive innumerable accidents, and disclose historical facts a thousand years after statues are crumbled away; and when nothing but the names of an Apelles or a Praxiteles remain. Does not a single medal of which we are in possession, give us greater light into hiscory, than the once famous libraries of Alexandria and Pergarnus, which are now no more? From these and many other considerations, I would willingly contribute my endeavours to render this study more general, and consequently more useful. I have tried a variety of methods to enable a young medalist to collect a cabinet, which may initiate him into the knowledge of medals and coins at a trifling expence. The method of taking off plaster-of-Paris and sulphur impressions, is known to every body: the first is too soft to preserve them from injury, and the brittleness of sulphur is a greater objection. I found by forming a coat or, layer of thin metal over the plaster-of-Paris, it would be a considerable defence. Tin is the cheapest and most convenient metal for the purpose, as it is sufficiently flexible, and at the same time very much resembles silver. The tin-foil I have tried, is of the same kind with that used for silvering looking-glasses. It should be laid over the medal or coin intended to be taken off, and then rubbed either with a brush, the point of a skewer, or a pin, till it has received perfectly, the impression of the medal; the tin-foil should now be pared off round the edge of the medal till it is brought to the same circumference: the medal must then be reversed, and the tin-foil will drop off into a chip box or mould ready to receive it, the concave side of the foil, or that which laid on the face of the medal, being uppermost; upon this pour plaster-of-Paris made in the usual manner, and when dry, the cast figure may be taken out of the box of mould, with the tin-foil sticking on the plaster, the convex side being now uppermost again, in which position it is to be kept in the cabinet, after it becomes dry. To have an impression very perfect, the thinnest tin-fuil should be made use of. The impressions taken in the foregoing manner almost equal silver medals in beauty, and are very durable. If the box or mould be rather larger than the impression of tinfoil , the plaster, when poured on runs round its edges, and forms a kind of white frame, or circular border round the foil, whence the new made medal appears more neat and beautiful. If this tin-foil be gilt with gold leaf, by means of thin isinglass glue, the medal will resemble gold. Having thus endeavoured to put it into the power of a young medalist to procure, in this manner, what number of medals and coins he pleases, for at most as many pence, I shall conclude, with only saying, that if by this means I may prove instrumental to the promotion of a more general knowledge thereof, by rendering the expence inconsiderable, it will be adequate to the motives of INVESTIGATOR 1771, Feb, |