328 SHAKESPEARIAN SUSPENSION BRIDGES. pressure of the atmosphere, 1500 pounds, will force the bucket, Se, up, so that the water will keep rising with the piston, M, at the same time the piston, N, will be forcing the water downwards. The water will, in consequence, force the bucket, a, so that the water in the barrel is forced out through the valve, 3, into the pipe, PP, and out at W. Now, it is easily to be perceived that an evacuation will be created at v; that afterwards the piston, N, will be raised, and the effect will be as described of M, and the effect on M as described of N, and so on alternately, so that a continual stream will flow out at W. The pressure of 1500 pounds is produced in consequence of the buckets, SS, being 20 feet from the level of the water; so that there is left five pounds on the square inch, which multiplied by 300 inches, the area of the bucket, gives 1500 pounds. The advantage of this pump is evident; as, whatever the winding of the mines might be, the pipe of such a pump might be turned accordingly, without any obstruction to the pump, and all the expense of cutting new shafts would thus be saved. We have already noticed more than once the ingenious Suspension Bridges of Coir Rope, recently introduced into India (see Mech. Mag. page 310, vol. 111.); and now quote, from the Calcutta Government Gazette, the following account of the metamorphosis of one of these bridges, at Allypore, into one of Sylhet cane, or ground rattans:”— "This curious change was, we understand, effected with ease in a few hours. The result is very interesting, inasmuch as it proves the great facility and economy with which these ingenious struc tures can be composed and suspended. "It appears that canes, from 100 to 225 feet in length, and from one to nearly two inches in diameter, are procurable on our northeastern frontier, merely for the cost of the labour in collecting them together. The Governor-General's agent, Mr. Scott, when at Sylhet, sent down to Calcutta, at the request of Mr. Colin Shakespeare, a supply of canes, coiled up like rope; and of which he has constructed the present small bridge, of 130 feet span by 5 feet in width. Not only the roadway, but all the radiating guys, catenary curved swings, preventer braces, and vertical suspenders, are of cane, none exceeding one and a quarter inch in diameter, and many not threequarters of an inch. "The use of iron thimbles throughout the composition gives an air of symmetry and neatness, while they greatly diminish friction, and add much to the strength of the bridge, which, like its rustic predecessor, has only one ironjointed arm in the centre. "The appearance of the arch is singularly light, even more so than rope; and it is in reality lighter as a whole, because the bamboo cross slips, forming the roadway, are lashed at once to the canes, and thus it becomes firmer than in the rope bridge, in which the treadway is distinct, and lies over the strands. PERCUSSION CANNONS AND GRENADES. two of the rains, and it is strongest when kept moist, the advantages gained to the country abounding in that useful and cheap commodity,will be incalculable; no bridge whatever, we believe, having been attempted in that quarter up to the present time. And we may conclude, that the natives, from habit and method in working up cane, will improve both on the neatness and strength of cane bridges now to be introduced, especially as they well know, from experience, how to choose the best kind of cane, and to cut it at the proper season for the purpose intended. 329 "The Right Hon. the GovernorGeneral visited the cane bridge, and his Excellency was pleased, after a minute inspection, to signify his approbation of so novel and useful a structure. "The original experimental Berai Torrent Bridge, still lying at Allypore under cover, was also exhibited to his Excellency, preparatory to its return to its station, for the third season of the approaching rains. It is then, we are told, the Postmaster General's intention that it shall be accompanied by a new bridge for a torrent a few miles west of Bancoorah." 330 MECHANICS THE MOST IMPORTANT BRANCH D, the conductor, showing the under side. If the conductor is fastened on in the manner shown in the sketch, it will fall off as soon as the fuse takes fire; if fastened with wire, it will keep on, and show but little light. The chamber of the fuse need not be primed, as the conductor will set fire to the composition. The outer line, E, is the size of a piece of cork, with a hole through it, which must be pressed down over the cap, and cut off well with the top of the cap, and which will secure the burr, at the bottom thereof, in the groove this is in case the cap is wanted to be kept on, ready for the grenade to be thrown at a moment's notice. The cork will yield to the blow when struck against metal, stone, or any other hard substance. I am, Sir, Your obedient servant, 11, Ordnance-place, Chatham. MECHANICS THE MOST IMPORTANT BRANCH OF NATURAL PHILOSOPHY. SIR,-The extensive application, in the present day, of mechanism and of mechanic power-the valuable Institutions which have been established for the cultivation of this science, and the universal encouragement with which it meets, mark the present as a great and important era in its history, and, at the same time, prove that, in a consideration of the relative value of the several branches of Natural Philosophy, Mechanics stands the first. The value and importance of any one of these is not to be determined by the grandeur or magnitude of the subject of which it treats, but by its applicability to the benefit, usefulness, and happiness of man, in the departments of agriculture, arts, manufactures, and commerce; the production of these is conceived to be the true test of their relative importance. If, in taking the three leading ones of astronomy, chemistry, mechanics, we were to judge of them by their grandeur and mag nitude, we should, perhaps, without hesitation, pronounce astronomy to be the first, probably chemistry to be the second, and mechanics the last; but if we view them by the foregoing test, in reference to the great objects of life, we shall not only alter, but exactly reverse this order. Man is in himself, indeed, a feeble creature, in comparison with what he effects; and how little of what he performs would he be able to accomplish without mechanical aid! To mechanics is agriculture indebted for the wheel, the various implements of husbandry, the plough, and the thrashing-machine; -manufactures, for the crane, the wheel, the screw, the wedge, and the various implements by which they are carried on; such as the pliers, the pincers, and the scissars, which are all modifications of the same principle. In the arts and in commerce, it is only necessary to point to our palaces, cathedrals, and bridges-our ships of war, and fleets of merchantmen; and from these to descend to the diminutive instrument of the key we turn in the lock, and the bit with which we curb the steed; and we shall find that, in every gradation between these vast extremes, the importance of mechanics is never for a moment suspended. Its value to commerce, in reference to the ship, is of a most striking description; the lever, the pulley, the wheel and axle, the wedge, the inclined plane, and the screw, are immediately suggested to the mind. The ship-builder lays down the keel, fixes in the timbers, and bends the stubborn plank by the application of mechanic power. Behold the stupendous body completely constructed! But it appears immoveably fixed. What hand, or accumulation of hands, can move it? Recourse is had to the screw and the inclined plane, and the ship slides majestically down the launches into her native element. The process of putting in the masts, rigging the ship, and taking in the cargo, are all carried on by the constant applieation of mechanic power. The ship is now ready for sea: by means of OF NATURAL PHILOSOPHY. the pulley the mariner hoists and spreads the powerful sails; she is ready to get under weigh, but the anchor is buried deep in the bed of the river; he has recourse to the windlass or capstan, and it is weighed with ease. Surely mechanics has done enough for the ship, or is she wholly dependent upon it? The gale swells the sails-she is rapidly impelled forward. But whither is she going? Already is she in danger of some rock or shoal. Behold the pilot at the helm (a lever), whose puny arm, with a facility that is truly astonishing, directs this vast body at his will. Aided by this stupendous power, "He steers the winged ship, and shifts the sails, Conquers the floods, and manages the gales." But, Sir, although this branch of natural philosophy is of so great importance, it is not to be considered as all in all. Natural philosophy is a community, of which its several branches are members, and each is essential to the whole. It reminds me of the Arabian Tale of the three brothers, enamoured of a princess, who was in a distant country: one possessed a telescope of extraordinary power; another a machine, by which he could, with the greatest velocity, transport himself to the most distant country; and the third, a certain elixir, which, if administered to the dying, would restore life. The brother who possessed the telescope was one day looking through it, and discovered the princess in the agonies of death; he instantly applied to the possessor of the extraordinary piece of mechanism, and they were all three immediately transported into the presence of the princess; the restorative was administered, and she was restored to life. Each, to obtain her hand, pleaded the importance of the art he possessed: "But for my telescope," said one, your illness would not have been discovered." "But for the machine," 66 331 said the other, "it would have been in vain that we saw your situation, for you must have expired before we could have arrived." "And both would have been perfectly useless," exclaimed the third, "unless I had possessed and administered the medicine which restored you to life." I shall not, Sir, trespass upon your valuable pages, to consider, in detail, the importance and value of astronomy and chemistry, of which there can be no doubt. I shall merely remark, that by means of the first we calculate time, the seasons, and their changes, and can steer with certainty through the pathless ocean; while, from the second, we derive the restorative and the anodyne, and a thousand useful combinations in the arts and manufactures. Nevertheless, I conceive, from what has already been shown, that it may be fairly concluded, that the power which enables man to build a ship to take him, in spite of winds and waves, into another hemisphere (there to exchange the products of agriculture, arts, and manufactures, and this to the advancement of his own happiness, comfort, and knowledge, and thereby the knowledge and civilization of the world,) that invests him with a power so gigantic, that, with it, there is scarcely a project which he can imagine, that he cannot thereby execute-is second in importance to no one of the various branches of natural philosophy. So stupendous, nay, infinite, is its principle, that Archimedes is said to have exclaimed, that if they would only find him a fulcrum on which to rest his lever, he would lift the world. The saying of that great mechanician may at least be considered as a figurative expression of the wonderful power which mechanics gives to man, and the effects which mechanics would one day produce in the world, in ages remote from that in which it was, as it were, prophetically uttered. I am, Sir, Let ABC be any triangle drawn between the parallel lines AB and ED; now, if on the base, AB, we draw any other triangle, as ABD, this triangle will be equal in superficial content or area to the triangle ABC. From the end of the base of the triangle, as A, draw AE parallel to BC, and also draw AF parallel to BD, of the triangle ABD; then we shall have two parallelograms, ABCE and ABDF, standing ou the same base, AB, and between the same parallels, AB and CD; then (by Cor. 2. of the last Theorem) these parallelograms are equal to each other; but the sides of the triangles, AC and AD, divide the parallelogram into two equal and identical triangles (by Theorem vII. Part 1); and hence the triangle ABC, being half the parallelogram ABCE, it is also half the parallelogram ABDF; but the triangle ABD is half the parallelogram ABDF, therefore it is equal to the triangle ABC, which was to be shown. COR. 1.-Hence, to measure a triangle, if we multiply the base by the perpendicular height, we shall have double the content of the triangle; hence we deduce the Rule for measuring triangles, viz. multiply the base by the perpendicular altitude, and half the sum is the area, or superficial content; or half the perpendicular altitude multiplied by the base, or half the base multiplied by the perpendicular altitude, will give the area. COR. 2. Hence, if on any given line we describe a parallelogram, and on the same base we describe a triangle, whose perpendicular height shall be equal to the width or height of the parallelogram, the triangle will be equal to half the parallelogram, or the parallelogram will be the double of the triangle. COR. 3.-Hence also triangles and parallelograms, on the same or equal bases, and lying between the same parallels (or of equal altitudes), are in proportion to cach other as 1 to 2. |