of scientific men in times past, and which are now admitted by all who take the trouble to investigate them, he has either never heard of, or chooses to set at nought without inquiry. The other class is that which finds capital. The projector, having perhaps exhausted his own funds, takes his scheme to some person who has a little money to spare, and dazzles him with the prospects of sudden and splendid wealth: little by little he is drawn into expenses which neither of them perhaps had anticipated. Failure after failure ensues, but still all is to be right at last. The fear of ridicule,—the necessity for retrieving, the one his capital, the other his credit,—these motives carry them on till the ruin of both puts a termination to their folly.

Unhappily, however, the stage is quickly occupied by other adventurers, profiting nothing by the fate of their precursors; and yet one would think that a very slight consideration of the subject would be sufficient to show the absurdity of the undertaking. What is the object aimed at? Is it to make a machine which, being once set in motion, shall go on without stopping until it is worn out? Every person engaged in the pursuit of the perpetual motion would perhaps accept this as a true statement of the object in view. Yet nothing is more easy than to make such a machine. There are from ten to twenty of them at work at this moment on the Rhine, opposite Mayence. These are water-mills in boats, which are moored in a certain part of the river; and, as the Rhine is never dry, these mills, which are simple in their construction, would go on for years,-go on, indeed, until they were worn out. But if this instance were mentioned, the projector would perceive that the statement of his object was imperfect. It must run thus: a machine which, being set in motion, shall go on till worn out without any power being employed to keep it in motion.

Probably few persons who embark in such a project sit down beforehand to consider thoroughly what it is they are about to undertake, otherwise it could hardly require much knowledge of mechanics to see the impossibility of constructing such a machine. Take as many shafts, wheels, pulleys, and springs as you please: if you throw them in a heap in the corner of your room, you do not expect them to move; it is only when put together that the wildest enthusiast expects them to be endowed with the power of self-movement; nor then unless the machine is set going. I never heard of a projector who expected his engine to set off the moment the last nail was driven, or instantly on the last stroke of the file. And why not? A machine that would continue to go of itself would begin of itself. No machine can be made which has not

some friction, which, however slight, would in a short time exhaust any power that could have been employed merely for the purpose of setting it in motion. But a machine, to be of any use, must not only keep moving itself, but furnish power; or, in other words, it must not only keep in motion, but it must have power to expend in some labor, as grinding corn, rolling metals, urging forward a vessel or a carriage; so that, by an arrangement of parts which of themselves have no moving power, the projector expects to make a machine, self-moving, and with the power of performing some useful task!

"Father, I have invented a perpetual motion!" said a little fellow of eight years old. "It is thus: I would make a great wheel, and fix it up like a water-wheel; at the top I would hang a great weight, and at the bottom I would hang a number of little weights; then the great weight would turn the wheel half round and sink to the bottom, because it is so heavy, and when the little weights reached the top, they would sink down because they are so many, and thus the wheel would turn round for ever." The child's fallacy is a type of all the blunders which are made on this subject. Follow a projector in his description, and if it be not perfectly unintelligible, which it often is, it always proves that he expects to find certain of his movements alternately strong and weak, not according to the laws of nature, but according to the wants of his mechanism.

If man could produce a machine which would generate the power by which it is worked, he would become a creator. All he has hitherto done,-all, I may safely predict, he ever will do,is to mould existing power so as to make it perform his bidding. He can make the waterfail in the brook spin his cotton, or print his book by means of machinery, but a mill to pump water enough to keep itself at work he cannot make. Absurd as it may seem, the experiment has been tried; but, in truth, no scheme is too absurd for adoption by the seekers after perpetual motion. A machine, then, is a mere conductor of power into a useful channel. The wind grinds the corn, the sails, the shafts, and the stones are only the means by which the power of the wind can be turned to that particular purpose; so it is the heat thrown out by the burning coal which performs all the multifarious operations of the steam engine, the machinery being only the connecting links between the cause and the effect.

Perhaps these remarks may induce any projector who has not yet begun, to pause on his enterprise; and may cause those who are about to advance their capital in such vain speculations, to ex amine the probabilities of a return for their outlay.

This ingenious contrivance, like the catamarans and massulah boats of Madras, is used for landing with safety through a heavy surf. The "Balsa," which is especially employed on the coasts of South America, both east and west, exhibits a remarkable instance of the ingenuity of the human mind in overcoming those obstacles which nature has raised to the prosecution of its pursuits. It is formed of two seal skins sewed up so as to form large bags from seven to nine feet in length; these, being covered with a bituminous substance so as to be perfectly air-tight, are inflated by flexible tubes and secured by ligatures; the pipe is of sufficient length to reach the mouth of the conductor of this frail bark, who is thus enabled occasionally to replenish the bladders with air, should any have escaped. The two are securely fastened together at one end, which forms the prow of the vessel; the other ends are spread about four feet apart by a small plank, and the raft completed with small sticks covered over with matting. The manager of the balsa sits well forward, with his passengers or goods close behind him, and armed with a double-bladed paddle approaches the back of the surf, waiting for the highest wave, and contrives to keep his baisa on the top of it with her bow towards the shore till she is thrown upon the beach to the very extent that the surf reaches, and the man immediately jumps off to secure his balsa

from returning with the sea, when the passengers land without wetting the soles of their shoes. The balsa will easily carry three passengers besides the person who guides it, and is employed in landing the cargoes from merchant vessels where the violence of the surf, particularly on the shores of the Pacific, prevents the possibility of European boats passing through it without great danger. Along the coast of Peru, which is almost entirely devoid of harbors, it is the only vessel used for these purposes, and by such frail means large bags of dollars and doubloons, and bars of silver and gold, are shipped off, without the least apprehension of their safe conveyance. Balsa, which is a Spanish word, means, in a nautical sense, float or raft; the above description applies only to that kind used at sea, but there is another balsa, more simple and more frail, used in crossing rivers, an account of which is thus given by Mr. Temple in his humorous and entertaining Travels in Peru: "Take a dried bullock's hide, pinch up each of the four corners, put a stitch with a thorn to keep those corners together, and your boat is made. For use, place it upon the water bottom downwards, then put one foot immediately in the centre, and let the other follow with the most delicate caution; you are now to shrink downwards, contracting your body precisely in the manner in which, probably, in your childhood, you have pressed a friar into a snuff-box. When crouched down in the bottom, sundry articles are handed in and ingeniously deposited round you, until the balsa sinks to about an inch or an inch and a half; it is then considered sufficiently laden. A naked peone (guide) now plunges into the stream, and, taking hold of one corner of the balsa, a peone on the shore imparts a gentle impulse to your tottering bark, while the person in the water, keeping hold of the corner with one hand, strikes out with the other, and swims away with you to the opposite bank." The work from which the above extract is made, is written in so facetious and lively a strain, at the same time giving such faithful and characteristic sketches of the customs of the country, that his readers cannot fail to receive amusement as wel' as instruction.

Automata.

An automaton is a piece of mechanism, made to resemble a living creature in outward appearance, and contrived so as to perform certain actions, resembling those of the being it represents. Both in ancient and modern times, the skill of ingenious men has been

directed to contrivances of this nature, some of which have dis played wonderful powers of invention, though in general little or no utility, unless so far as they were sources of public amusement, and examples of what may be accomplished by reflection and long perseverance. Brewster, in his Natural Magic, has given a very full account of the most remarkable automata, from which this article is principally taken.

The

Mechanical automata of the ancients.-The ancients had attained some degree of perfection in the construction of automata. tripods which Homer mentions as having been constructed by Vulcan for the banqueting-hall of the gods, advanced of their own accord to the table, and again returned to their place. Self-moving tripods are mentioned by Aristotle, and Philostratus informs us, in his Life of Apollonius, that this philosopher saw and admired similar pieces of mechanism among the sages of India.

Automata of Dadalus.-Dædalus enjoys also the reputation of having constructed machines that imitated the motions of the hu man body. Some of his statues are said to have moved about spontaneously, and Plato, Aristotle, and others have related that it was necessary to tie them, in order to prevent them from running away. Aristotle speaks of a wooden Venus, which moved about in consequence of quicksilver being poured into its interior; but Callistratus, the tutor of Demosthenes, states, with some probability, that the statues of Dædalus received their motion from the mechanical powers. Beckmann is of opinion that the statues of Dædalus differed only from those of the early Greeks and Egyptians in having their eyes open and their feet and hands free, and that the reclining posture of some, and the attitude of others, "as if ready to walk," gave rise to the exaggeration that they possessed the power of locomotion. This opinion, however, cannot be maintained with any show of reason; for if we apply such a principle in one case, we must apply it in all, and the mind would be left in a state of utter skepticism respecting the inventions of ancient times.

Wooden pigeon of Archytas.-We are informed by Aulus Gellius, on the authority of Favorinus, that Archytas of Tarentum, who flourished about four hundred years before Christ, constructed a wooden pigeon which was capable of flying. Favorinus relates, that when it had once alighted, it could not again resume its flight; and Aulus Gellius adds, that it was suspended by balancing, and animated by a concealed aura or spirit.

Automatic clock of Charlemagne.-Among the earliest pieces of modern mechanism was the curious water-clock presented to Charlemagne by the Kaliph Harun al Raschid. In the dial-plate