“The Indian, on his return home, carefully suspends his blow-pipe from the top of his spiral roof; seldom placing it in an oblique position, lest it should receive a cast.”--Waterton’s Wanderings in South America, p. 58.
Note 11, p. [96].--Pendulum and spring.
A clock is nothing more than a piece of machinery to maintain the action of the pendulum, and at the same time to count and register the number of its oscillations; and by that peculiar property, that one vibration commences exactly where the last terminates, no part of time is lost or gained in the juxtaposition of the units so counted.
If some extraneous force were not applied, in a clock or watch, to maintain or perpetuate the natural vibrations of a pendulum, or oscillations of a balance, they would soon come to rest, by reason of friction in the mechanism, and the resistance opposed by the air to the parts in motion. This force, in the larger clocks, is usually a suspended weight; but, in the portable clock and watch, it is a spring coiled in a metallic box, that actuates the wheel-work by gradually unbending itself.
In the former of these cases, the weight is suspended by a cord or chain that is coiled round a cylinder when wound up, which cylinder being of uniform diameter throughout its length, is acted on by the cord, when fast at the interior end, by a similar force in every situation; and, therefore, imparts through the train, connected with its great wheel, invariable impulses to the escapement-wheel, at every vibration of the pendulum; which pendulum receives therefrom such a slight push, as is just sufficient to restore the momentum which it loses from friction and the air’s resistance, and thus the uniform motion of the pendulum is perpetuated. But when a spring is substituted for a weight, it is clear that its agency cannot be uniform, since, as the reader will learn by turning to page 101, it is a general law that elastic bodies, in the recovery of their form, after the removal of the compressing force, exert a greater power at first than at last, so that the whole progress of restoration is a retarded motion. It, therefore, became necessary to introduce some mechanical contrivance which might equalize such motion. This correction is effected by an apparatus termed a FUSEE, and is nothing more than the application of the wheel and axle; it is that conical barrel seen in most watches round which the chain coils in the act of winding up. When the fusee is full of chain, or the watch is wound up, the spring, through the medium of the chain, will act upon its upper part, which being very near the centre will give the spring but little power; but, as the spring uncoils and diminishes in strength, it will act upon a larger part of the fusee, until at last it gets to the bottom of it, and consequently, if the several increasing grooves upon it are made to increase in the same proportion as the power of the spring decreases, an equable force must be obtained.
Springs may be thus said to afford the means of packing up force, to be used whenever it is required. Mr. Babbage observes that the half minute which we daily devote to the winding up our watches is an exertion by which we pack a quantity of force, which is gradually expended during the ensuing twenty-four hours. Springs then will enable us to avail ourselves of inconstant and variable forces which must otherwise remain incapable of useful application, and the period may arrive when force will thus become an article of traffic, and machines be sent to the windmill to be wound up. The manner in which force is constantly allowed to run to waste is quite extraordinary in the present advanced state of science. We need only look at the working of the treadmill. The public are little aware of the enormous sums annually expended in towing vessels by steam from the Nore to the port of London; were floating treadmills established, the labour of those, upon whom punishment has been awarded, might be rendered available to the most important interests; whereas, with the present system, not only is this labour entirely lost, but is actually a source of expense, for machines, with all the accompaniments of engineers, are provided to counterbalance the force so uselessly generated.
Note 12, p. [97].--Elastic chairs and beds.
The elastic property of iron springs has been lately exemplified in a very striking manner, by the invention of Pratt’s elastic chairs and beds; which, instead of the usual stuffing of feathers, are filled with iron wire!!! which is twisted into spiral form. Down itself cannot be more gentle or springy; it yields to pressure, and yet never becomes lumpy: beds thus constructed have the advantage of not heating the body; and, above all, they never require to be shaken or “made.” Had Vulcan fortunately made such a discovery before his ejectment from Olympus, his wife, Venus, would surely never have treated him with that contempt which mythologists have recorded of her; while her priestesses, the housemaids, must, in gratitude, have been bound to extend their protection to a benefactor, who could save them so much daily labour. For particulars of this curious invention, the reader may consult the Literary Gazette for March 17, 1827.
Note 13, p. [98].--Duck and drake.
The phenomenon has been explained as depending upon the inertia of the parts of matter, which renders a certain time necessary in order to communicate to any body a sensible motion; so that when a body, moving with considerable velocity, meets with another of much greater size, it experiences almost as much resistance as if the latter were fixed. Nothing is easier to be divided than water; yet, if the palm of the hand be struck with some velocity against its surface, a considerable degree of resistance, and even of pain, is experienced from it, as if a solid body had been struck; nay, a musket ball, when fired against water, is repelled and even flattened by it. In like manner, if we load a musket with powder, and, instead of a ball, introduce a candle, and fire it against a board, the latter will be pierced by the candle end, as if by a ball. The cause of this phenomenon, no doubt, is, that the rapid motion with which the candle end is impelled, does not allow it time to be flattened, and therefore it acts as a hard body.