This effect of the pellicle reminded him of that of a drop of oil, which, as Venturi observed, suddenly paralysed the motions of the camphor, when dropped upon any part of the aqueous surface. Dissatisfied, however, with the explanations of this singular fact, M. Serullas supposes, that the camphoric emanation was dissolved by the oily substances expanded over the water, and that this dissolution taking place on every part of the chain, formed by the camphoric molecules, propagates itself more and more, and prevents the reaction which produces the motion. The inactivity of camphor placed upon water impregnated with a fat matter, he explains in a similar man

ner.

On the Motions of the Alloy of Potassium and Bismuth upon Mercury.

This alloy moves with great volubility on a bath of mercury, whether it be covered with water or not. In both cases it exhales such a strong smell of garlic or phosphorus, that it cannot be ascribed merely to the small quantity of arsenic in the bismuth, but to a particular modification of the hydrogen produced.

M. Serullas remarks, that during the decomposition of this alloy upon mercury, it forms at the surface of the bath a black pellicle, (found by analysis to be a mixture of the oxide of bismuth and charcoal); that this pellicle is attracted by metallic substances, and not by those which are not metallic; that if a plate or rod of zinc, iron, copper, brass, silver, or even bismuth, touches the water of the bath, no attraction is exhibited, but that if it penetrates to the mercury, the black matter springs upon the metal with the rapidity of lightning, and even to a great distance,-a phenomenon which he ascribes to the electric state of the black matter.

The agitation of the alloy of potassium and bismuth, does not appear to him to be owing to the amalgamations of the potassium, but to the disengagement of hydrogen, resulting from the decomposition either of the atmospheric water, whose accumulation round each fragment becomes instantly visible, or of that contained in mercury, more or less moist.

M. Serullas ascribes the impetuosity with which potash moves upon water to the rapid emission of the hydrogen which is produced. In order to prove this, he put portions of the alloy of potassium and bismuth under a receiver of dry atmospheric air, and reversed upon dry mercury, the alloy remained stationary, and was quietly dissolved in the mercury. Other pieces were placed in the same manner under another receiver, and were left for a sufficient time to establish their immoveability. As soon as two drops of water were thrown into the air across the mercury, the fragments began to move with their accustomed velocity. The same effect was obtained by substituting in place of atmospheric air dry azote, or oxygen equally dried. Similar results were obtained by substituting potassium in place of the alloy. M. Serullas now placed a capsule containing mercury, upon which he had put some fragments of the alloy, and having introduced it under the receiver of an air-pump, the fragments instantly expired as soon as the air was withdrawn, and were reanimated by its introduction.

On the Motion of the Alloys of Potassium and Lead, Potassium and Tin, and Potassium and Iron, upon Mercury.

The two first of these alloys are decomposed with difficulty when in contact with water. No doubt, however, the serrated contexture of these metals protects the potassium from the aqueous fluid. When they are thrown on mercury, however, they are soon set in agitation, their motion gradually increases, and they acquire a still greater velocity, if water is poured upon it.

When the alloys have disappeared from the surface of the bath, and have left only a black and unctuous water, M. Serullas observed, that they occasioned starts which raised the pellicle with a species of explosion, and he supposed this to be part of the amalgamated potassium which decomposed the water in the mass of mercury.

M. Serullas likewise remarked, that the alloy of potassium and iron turns like the other alloys upon a bath of mercury covered with water; and he informs us, that all that he has said of the alloys of potassium is equally applicable to those of sodium.

ART. XXX.-An attempt to Analyse the Automaton Chess Player of M. De Kempelen.

THE title prefixed to this article, is that of a very interesting and ingenious little work, just published, which has scarcely reached us in time to enable us to present a satisfactory analysis of it to our readers.

The Automaton Chess Player of Kempelen was introduced into England by its inventor in 1783, and has, during the last two years, been exhibited in various parts of England and Scotland, under the direction of M. Maelzel. The interest which it excited is fresh in our recollection; and the public opinion is pretty equally divided between the two theories, of its being a piece of real machinery, directed by the exhibitor, or a piece of ingenious deception, under the controul of an internal agent. If the impossibility of a chess-player being concealed in the machine had been thoroughly established, we should have had no hesitation in considering magnetism as the moving power; but a very narrow inspection of the apparatus soon satisfies us that there is room for a living being; and that while this appeared to be the case, there was no occasion for calling in the aid of more complex machinery.

The author of the present work has, we think, demonstrated the truth of this opinion, with a degree of sagacity and ingenuity of no ordinary amount; and he has shewn, by a series of drawings, how a full grown man may be concealed in the machine, and may take the successive positions which are rendered necessary during the preliminary stratagem, as well as during the progress of the game. We shall endeavour, in the following extracts, to exhibit the principal arguments which he employs. "The annexed drawings, (Plate X. Figɛ, 1. and 2.) represent the general appearance of the machine. It runs on castors, and is either seen on the floor when the doors of the apartment are thrown open, or is wheeled into the room at the commencement of the exhibition.

"The exhibitor, in order to shew the mechanism, as he informs the spectators, unlocks the door (A, Fig. 1.) of the chest, which exposes to view a small cupboard, lined with black or dark coloured cloth, and containing different pieces of machinery, which seem to

occupy the whole space. He next opens the door (B, Fig. 2.) at the back of the same cupboard, and holding a lighted candle at the opening, still further exposes the machinery within. The candle being withdrawn, the door (B) is then locked. The drawer (G, G, Fig. 1.) in the front of the chest is then opened, and a set of chess men, a small box of counters, and a cushion for the support of the Automaton's arm, are taken out of it. The exhibitor now opens the two front doors (C C, Fig. 1.) of the large cupboard, and the back door (D, Fig. 2.) of the same, and applies a candle, as in the former case. This cupboard is lined with cloth like the other, but it contains only a few pieces of machinery. The chest is now wheeled round, the garments of the figure lifted up, and the door (E, Fig. 2.) in the trunk, and another (F,) in the thigh, are opened. But it must be observed, that the doors (B and D) are closed.

"The chest is now restored to its former position on the floor; the doors in front, and the drawer, are closed and locked; and the exhibitor, after he has occupied some time at the back of the chest, in apparently adjusting the machinery, removes the pipe from the hand of the figure, winds up the works, and the Automaton begins to move."

After pointing out the extreme difficulty of exccuting the movements of the chess player by machinery alone, and the extreme probability of a deception, from the eagerness of the exhibitor to display a part of the mechanism at one time, and his studied concealment of it at another, our author deduces an argument in favour of his opinion, from the regular and undeviating mode of disclosing the interior of the chest; and he shews that the various facts which have been observed respecting the winding up of the machine, " afford positive proof that the axis turned by the key is quite free and unconnected either with a spring or a weight, or any system of machinery."

The author then proceeds to point out a method by which any person well skilled in the game, and not exceeding the ordinary stature, may secretly animate the automaton, and imitate the movements of the chess-player. This method will be easily understood from the following extract:

"The drawer (G G, Fig. 10.) when closed, does not reach to the back of the chest; it leaves a space (O) behind it, about 1 foot 2 inches broad, 8 inches high, and 3 feet 11 inches long. This space is never exposed to view.

"The small cupboard is divided into two parts by the door or screen (I, Fig. 6.) which is moveable on a hinge, and is so contrived that when B is closed, this screen may be closed also. The machinery (H) occupies the whole of the front division as far as I; the

hinder division is nearly empty, and communicates with the space behind the drawer, the floor of this division being removed.

"The back of the great cupboard is double, and the part (P, Q,) to which the quadrants, &c. are attached, moves on a joint (Q), at the upper part, and forms, when raised, an opening (S) between the two cupboards, by carrying with it part of the partition (R), which is composed of cloth stretched tight. Fig. 10. shews the false back closed. Fig. 11. shews the same raised, forming the opening (S) between the chambers.

"When the trunk of the figure is exposed by lifting up the dress, it will be seen that a great part of it is occupied by an inner trunk (N), which passes off towards the back in the form of an arch, (Fig. 2.) and conceals a portion of the interior from the view of the spectators. This inner trunk opens to the chest by an aperture (T, Fig. 9.) about 1 foot 3 inches high, by 1 foot broad.

"When the false back is raised, the two chambers, the trunk, and the space behind the drawer, are all connected together.

"The player may be introduced into the chest through the sliding panel (U, Fig. 6.), at the end. He will then elevate the false back of the large cupboard, and assume the position represented by the dotted lines in Figs. 3. and 4. Every thing being thus prepared, "the charm's wound up," and the exhibitor may begin his operations by opening the door (A). From the crowded and very ingenious disposition of the machinery in this cupboard, the eye is unable to penetrate far beyond the opening, and the spectator is led to conclude that the whole space is occupied with a similar apparatus. This illusion is strengthened and confirmed by observing the glimmering light which plays among the intricacies of the machinery, and occasionally meets the eye, when the lighted candle is held at the door (B). A fact, too, is ascertained, which is equally satisfactory, though for opposite reasons, to the spectator and the exhibitor, viz. that no opake body of any magnitude is interposed between the light and the spectator's eye. The door (B) must now be locked, and the screen (I) closed, which being done at the moment the light is withdrawn, will wholly escape observation.

"It has been already mentioned, that the door (B), from its construction, closes by its own weight; but as the player's head will presently be very near it, the secret would be endangered, if, in turning round the chest, this door were, by any accident, to fly open; it becomes necessary, therefore, " to make assurance double sure," and turn the key. If the circumstance should be observed, it will probably be considered as accidental, the keys being immediately wanted for the other locks.

"The opening (B) being once secured, and the screen (1) closed, the success of the experiment may be deemed complete. The secret is no longer exposed to hazard; and the exhibitor is at liberty to shape his conduct in any way he may think most likely to secure the confidence of the spectators, and lead them insensibly from the main object of pursuit. The door (A) may safely be left open; this will tend to confirm the opinion, which the spectators probably formed on viewing the candle through this cupboard, that no per