The case was urgent, and the means of restoration to health, however desperate, must be adopted. With a heavy sigh, Maelzel told down the cash; and never had the Automaton played with so much inward unction as he did that morning. The king declined compromising royalty by entering the lists himself; but placed his minister-of-war in the opposition chair, and graciously conde. scended to offer his royal advice in each critical situation of the pieces. The coalition was beaten, and the surrounding courtiers, of course, attributed defeat solely to the bad play of the ministerof-war!

Chinese Bamboo Irrigation-wheel.

The Chinese irrigation-wheel, which is turned by the current of the stream, varies from twenty to thirty feet or more in height, according to the elevation of the bank; and when once erected, a constant supply of water is poured by it into a trough, on the summit of the river's side, and conducted in channels to all parts of the sugar plantations. One is at a loss which most to admire, the cleverness and efficiency, or the cheapness and simplicity of the contrivance.

The props of the wheel are of timber, and the axis is a cylinder of the same material; but every other portion of the machine exhibits some modification or other of the bamboo, even to the fastenings and bindings, for not a single nail or piece of metal enters into its composition. The wheel consists of two rims of unequal diameter, of which the one next the bank is rather the least. "This double wheel," observes Staunton, "is connected with the axis by sixteen or eighteen spokes of bamboo, obliquely inserted near each extremity of the axis, and crossing each other at about two-thirds of their length. They are there strengthened by a concentric circle, and fastened afterwards to the rims; the spokes inserted in the interior extremity of the axis. (or that next to the bank,) reaching the outer rim, and those proceeding from the exterior extremity of the same axis reaching the inner and smaller rim. Between the rims and the crossings of the spokes is woven a kind of close basket-work, serving as ladle-boards," which are acted upon by the current of the stream, and turn the wheel round.

The whole diameter of the wheel being something greater than the height of the bank, about sixteen or twenty hollow bamboos, closed at one end, are fastened to the circumference, to act as buckets. These, however, are not loosely suspended, but firmly attached with their open mouths towards the inner or smaller rim

of the wheel, at such an inclination, that when dipping below the water their mouths are slightly raised from the horizontal position; as they rise through the air their position approaches the upright sufficiently near to keep a considerable portion of the contents within them; but, when they have reached the summit of the revolution, the mouths become enough depressed to pour the water into a large trough placed on a level with the bank to receive it. The impulse of the stream on the ladle-boards at the circumference of the wheel, with a radius of about fifteen feet, is sufficient to over. come the resistance arising from the difference of weight between the ascending and descending, or loaded and unloaded, sides of the wheel. This impulse is increased, if necessary, at the particular spot where each wheel is erected, by damming the stream, and even raising the level of the water where it turns the wheel. When the supply of water is not required over the adjoining fields, the trough is merely turned aside or removed, and the wheel con. tinues its stately motion, the water from the tubes pouring back again down its sides. These wheels extend, on the river Kan-keang, from the neighborhood of the pass to a considerable distance down | its stream towards the lake, and they were so numerous that we never saw less than thirty in a day. It is calculated that one of them will raise upwards of three hundred tons of water in the four. and-twenty hours. Viewed merely in regard to their object, the Persian wheel, and the machines used for raising water in the Tyrol, bear some resemblance to the one just described, but, as observed by Staunton, "they are vastly more expensive, less sim ple in construction, as well as less ingenious in contrivance."

Discovery of Gunpowder, and Inventions arising therefrom. It is not known with accuracy at what time gunpowder was discovered. The Chinese were acquainted with it at a very early period. It was not until the beginning of the sixteenth century, one hundred and fifty years after the invention of cannon, that iron balls were used. Muskets were not used until the year 1521. The Spaniards first armed their foot soldiers in this manner. They used matchlocks: firelocks were not used until the beginning of the seventeenth century,—that is, one hundred and eighty years after muskets were invented. Even then, the great Marshal Saxe had so little confidence in the efficacy of a flint, that he ordered a matchlock to be added to the lock with a flint, lest the flint should miss fire: such is the force of habit on the human mind. Bayonets derive their name from the town of Bayonne, in France, where

they were introduced about 1673. They came in use among the English grenadiers in the reign of James the Second. Many such are yet to be seen in the small armory at the Tower of London. The use of them, fastened to the muzzle of the firelock, was also a French improvement, first adopted about 1690. It was accompanied in 1693, at the battle of Marseille, in Piedmont, by a dread. ful slaughter, and its use universally adopted by the rest of Europe in the war of the succession.

A few Remarks on the Relation which subsists between a Machine and its Model.

The following remarks by Edward Sang, a teacher of mathematics in Edinburgh, are very interesting, as demonstrating the relation between a machine and its model,—a subject which is, perhaps, not generally well understood:

"At first sight, a well-constructed model presents a perfect representation of the disposition and proportion of the parts of a machine, and of their mode of action.

"Misled by the alluring appearance, one is apt, without entering minutely into the inquiry, also to suppose that the performance of a model is, in all cases, commensurate with that of the machine which it is formed to represent. Ignorant of the inaccuracy of such an idea, too many of our ablest mechanicians and best workmen waste their time and abilities on contrivances which, though they perform well on the small scale, must, from their very nature, fail when enlarged. Were such people acquainted with the mode of computing the effects, or had they a knowledge of natural philosophy, sufficient to enable them to understand the basis on which such calculations are founded, we should see fewer crude and impracticable schemes prematurely thrust upon the attention of the public. This knowledge, however, they are too apt to regard as unimportant, or as difficult of attainment. They are startled by the absurd distinction which has been drawn between theory and practice, as if theory were other than a digest of the results of experience; or, if they overcome this prejudice, and resolve to dive into the arcana of philosophy, they are bewildered among names and signs, having begun the subject at the wrong end. That the attainment of such knowledge is attended with difficulty is certain, but it is with such difficulty only as can be overcome by properly directed application. It would be, indeed, preparing disappointment to buoy them up with the idea, that knowledge, even of the most trivial importance, can be acquired without labor.

Yet it may not be altogether unuseful, for the sake both of those who are already, and of those who are not, acquainted with these principles, to point out the more prominent causes, on account of which the performance of no model can, on any occasion, be considered as representative of that of the machine. Such a notice will have the effect of directing the attention, at least, to this important subject. In the present state of the arts, the expense of constructing a full-sized instrument is, in almost every instance, beyond what its projector would feel inclined, or even be able, to incur. The formation of a model is thus universally resorted to, as a prelude to the attempt on the large scale. An inquiry, then, into the relation which a model bears to the perfect instrument, can hardly fail to carry along with it the advantage of forming a tolerable guide, in estimating the real benefit which a contrivance is likely to confer upon society.

"In the following paper I propose to examine the effect of a change of scale on the strength and on the friction of machines, and, at the same time, to point out that adherence to the strictest principles which is apparent in all the works of nature, and of which I mean to avail myself in fortifying my argument.

"Previous, however, to entering on the subject-proper, it must be remarked that, when we enlarge the scale according to which any instrument is constructed, its surface and its bulk are enlarged in much higher ratios. If, for example, the linear dimensions of an instrument be all doubled, its surface will be increased four and its solidity eight-fold. Were the linear dimensions increased ten times, the superficies would be enlarged one hundred, and the solidity one thousand times. On these facts, the most important which geometry presents, my after-remarks are mostly to be founded.

"All machines consist of moveable parts, sliding or turning on others, which are bound together by bands, or supported by props. To the frame-work I shall first direct my attention.

"In the case of a simple prop, destined to sustain the mere weight of some part of the machine, the strength is estimated at so many hundred weights per square inch of cross section. Sup. pose that, in the model, the strength of the prop is sufficient for double the load put on it, and let us examine the effect of an enlargement, ten-fold, of the scale according to which the instrument is constructed. By such an enlargement, the strength of the prop would be augmented one hundred times; it would be able to bear two hundred loads such as that of the model, but then the weight to be put on it would be one thousand times that of the small ma. chine, so that the prop in the large machine would be able to bear

only the fifth part of the load to be put on it. The machine, then, would fall to pieces by its own weight.

"Here we have one example of the erroneous manner in which a model represents the performance of a large instrument. The supports of small objects ought clearly to be smaller in proportion than the supports of large ones. Architects, to be sure, are accustomed to enlarge and to reduce in proportion; but nature, whose structures possess infinitely more symmetry, beauty, and variety, than those of which art can boast, is content to change her proportions at each change of size. Let us conceive an animal having the proportions of an elephant and only the size of a mouse; not only would the limbs of such an animal be too strong for it, they would also be so unwieldy that it would have no chance among the more nimble and better proportioned creatures of that size. Reverse the process, and enlarge the mouse to the size of an elephant, and its limbs, totally unable to sustain the weight of its immense body, would scarcely have strength to disturb its position even when recumbent.

"The very same remarks apply to that case in which the weight, instead of compressing, distends the support. The chains of Trinity Pier are computed to be able to bear nine times the load put on them. But if a similar structure were formed of ten times the linear dimensions, the strength of the new chain would be one hundred times the strength of that at Trinity, while the load put upon it would be one thousand times greater; so that the new structure would possess only nine-tenths of the strength necessary to support itself. Of how little importance, then, in bridge building, whether a model constructed on a scale of perhaps one to a hundred support its own weight! Yet, on such grounds, a proposition for throwing a bridge of two arches across the Forth, at Queensferry, was founded. Putting out of view the road-way and passengers altogether, the weight of the chain alone would have torn it to pieces. The larger species of spiders spin threads much thicker, in comparison with the thickness of their own bodies, than those spun by the smaller ones. And, as if sensible that the whole energies of their systems would be expended in the frequent reproduction of such massy webs, they choose the most secluded spots; while the smaller species, dreading no inconvenience from a frequent renewal of theirs, stretch them from branch to branch, and often from tree to tree. I have often been astonished at the prodigious lengths of these filaments, and have mused on the immense improvement which must take place in science, and in strength of materials too, ere we could, individually, undertake works of such comparative magnitude.