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from an already organized base of railways at home; the material for the Indian lines had to be borne over thousands of miles of a sea voyage. The construction of the Indian railways has presented difficulties of a much more formidable character than those which have been met with on the Pacific line. It is true that this railway has been carried over vast plains and mountain ranges of which little was known, and in the face of the attacks of hostile Indian tribes. In India, the works were carried out in the face of difficulties connected with the oppressive heat of the climate; through forests and jungles which were the resort of savage animals, and the people employed were natives of the country, speaking a language unknown to those by whom they were employed, and whose habits and modes of life unfitted them for labor such as that on which they were engaged. Great works such as those of the Bhore Ghaut and Thull Ghaut inclines presented difficulties equal to, if not greater, than any experienced in the crossing over the Rocky Mountains. Streams wider and more rapid than met with between Omaha and San Francisco have been successfully bridged, and present some of the greatest triumphs of modern engineering science. — Engineering.

ON ROADS AND RAILWAYS IN NORTHERN INDIA AS AFFECTED BY THE ABRADING AND TRANSPORTING POWER OF WATER.

Mr. Login, at the meeting of the British Association, commenced by stating general conclusions he had arrived at, to the effect that the abrading and transporting power of water was increased directly as the velocity and inversely as the depth; also, that when flowing water had once got its proper load of solid matter in suspension all erosive action ceased. In short, that it was like a balance, the load being always equal to the power, which power, somehow or other, increased as the velocity became greater, and decreased as the depth of a stream increased, Nature always adjusting the load to the various circumstances. He then gave a short description of the plains and rivers of Northern India, and, by the aid of diagrams, went on to argue that rivers flowing through alluvial plains were raising rather than lowering their beds, and, though this silting-up process may be very slow, yet it was satisfactory to the engineer to know that the foundations of his bridges would be as safe, if not safer, a hundred years hence, as they are now. In speaking of the changes of the course of rivers, he said that there was more or less a constant cutting going on, on the concave banks of a river, with a tiltingup process on the opposite side. The next subject referred to was the denudation of the high level plains of Northern India called "Doabs (two waters), and locally known by the name of Bhanger" land, in contradistinction to the term " Khadir," or low valley lands, through which the large rivers, fed by the melting snows, now meander. Mr. Login said that the higher ridges, or "back bones," of these Doabs were not caused by any upheavals, but were formed by the denudation of these high level

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plains; and, as the rainfall was three or four times as great in the valley of the Ganges as that of the Indus, these back bones in the plains of the Punjaub disappeared, as well as all defined drainage lines some 50 miles below the hills, for the simple reason that the water spread over these plains and was absorbed. To this peculiarity in the Punjaub particular attention was drawn; for Mr. Login argued that, if standing crops and grass could permit, without receiving injury, the rain which fell higher up to flow through rather than over those standing crops, surely the same water could flow over an iron rail at very slow velocities, seldom, if ever, rising to such a height as to interfere with a locomotive passing over the line; however, if it did, the obstruction could only last for not more than one day in a whole year. By acting on this principle, Mr. Login believed that hundreds of thousands of pounds can be saved in the construction of railways in Upper India, as no embankments or masonry culverts and bridges would be required in crossing such high level plains as the Bechna doabs, which he had surveyed; while, by pounding back those flood-waters by embankments, and forcing it to find an escape through culverts, was more costly and dangerous, for it increased the abrading and transporting power of the water, at the very point where alone it could do injury, namely, where it crossed the rail. In support of his arguments he quoted actual occurrences. He urged that deep foundations for bridges was the proper mode for spanning the large rivers of India, and that only the opening for both the main stream and the inundation water should be provided, while any little water that might be left behind in the swamps, or low ground which is below the level of the main river, should be drained off by what he calls" spoon-mouthed syphons." Speaking of the minor torrents, he briefly referred to another description of bridge, resting on "inverts," with deep, massive curtain walls, which may, with economy, be introduced in some instances; and concluded by stating that once the abrading and transporting power of water was more fully investigated, the engineer could proceed with all descriptions of works affected by flowing water with greater confidence and economy, instancing harbors on the Madras coast, which province, from being at present a financial loss to the State, would soon become profitable, both to India and England, by increased commerce.

COMMUNICATION BETWEEN GUARD, DRIVER, AND PASSENGERS.

Mr. S. Varley, at the meeting of the British Association, read a paper "On a System of Communication between Guards and Passengers on Railway Trains when in Motion." The system was applied in 1866, and is now in use on the Royal train, and it has since been adopted in other trains. He believed electricity to be the best agent for signalling on rolling stock, and the difficulty in applying it, he believed, was more with reference to the mechanical parts than the electrical. Three electrical systems had been applied to railway travelling: one used by Mr. Preece, on the

South-Western Railway; one by Mr. C. V. Walker, on the Great Eastern Railway, applied to trains which run 20 miles without stopping; and one by Mr. Martin on the North-Western Railway; and this was the one which formed the subject of this paper. Insulated wire is run underneath the carriages, and the iron works, the coupling bars, and the wheels are connected electrically together. Two insulated wires (one of which is connected with the wire underneath the carriages, the other to the iron work) are led up to each compartment, and when these two wires are brought in contact the telegraphic circuit is closed, and the alarum set ringing. The carriages are connected together by means of flexible conductors, and these are also laterally connected with the insulated wire underneath the vehicles. The apparatus in the guard's van consists of a battery placed in a box, and an electric alarum, and on the engine is another alarum. By moving a handle in any of the carriages the alarums are set going. The action of moving the handle sets free a spring, and the handle is locked, and cannot be put in its original position until the spring or lock is opened, which is done by means of a key in the possession of the guard. No electrical knowledge is needed to work or keep in order the apparatus; the maintenance of it is not costly, and the alarums, batteries, etc., can be easily shifted from one train to another. At the request of the Board of Trade, in 1866 a train was fitted up with this apparatus, which had travelled 250 miles each day, and been started and stopped by its means. Mr. H. Palmer, M.P., said that, in the House of Commons, Mr. Bright said the rope system merely a rope running above the door of the carriage, with no communication with the insidewas the best, and at the same time simplest and cheapest system, but it had been adopted on the North-Eastern Railway, and had been found to be very inefficient. He wished to know what investigations the various systems had undergone by the Board of Trade, and whether this system was actually in use on the railway. Mr. Parkes agreed as to the inefficiency of the rope system. Mr. Varley, in reply, said the various plans were tried at York. The cord system failed, inasmuch as it was not detective of the person giving the alarm. His apparatus had been tested daily for two years, the train being started with it, and it had worked regularly. As a practical proof of the uselessness of the cord communication, he might state that it was attached to the train that took them to Plymouth, when it was pulled but failed to attract attention. He believed it was only adopted to satisfy public opinion.

THE CHANNEL RAILWAY.

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J. F. Bateman, F.R.S., at the meeting of the British Association, read a paper on The Channel Railway." He referred at some length to the advantages which would accrue from a continuous railway communication between England and France, and to the various proposals for effecting that object by a tunnel to be

driven beneath the bed of the sea; by submerged roadways and tubes; by large ferry-boats carrying trains on board; and by bridges to be carried on piers formed on islands to be sunk in the Straits. A ferry-boat, large enough to receive a whole ordinary train on board, would be a material improvement on the present means of conveyance. Such boats cannot, however, be employed, except by the construction of special harbors on each coast. With reference to a tunnel, it has been proposed to drive one of ordinary size for a double line of railway, which shall descend by a gradient of one in 60 on each side of the channel to a depth of about 270 feet below the bed of the sea. The total length of the tunnel would be 30 miles, of which 22 would be beneath the sea. A special commission, appointed by the Emperor of the French, recently reported in favor of a submarine tunnel. We propose to lay a tube of cast iron on the bottom of the sea, between coast and coast, to be commenced on one side of the channel, and to be built up within the inside of a horizontal cylinder, or bell, or chamber, which shall be constantly pushed forward as the building up of the tube proceeds. The bell or chamber within which the tube is to be constructed will be about 80 feet in length, 18 feet internal diameter, and composed of castiron rings 8 inches thick, securely bolted together. The interior of the bell will be bored out to a true cylindrical surface, like the inside of a steam cylinder. The tube to be constructed within it will consist of cast-iron plates, in segments 4 inches in thickness, connected by flanges, bolted together inside the tube, leaving a clear diameter of 13 feet. Surrounding this tube, and forming part of it, will be constructed annular discs or diaphragms, the outside circumference of which will accurately fit the interior of the bell. These diaphragms will be furnished with arrangements for making perfectly water-tight joints, for the purpose of excluding sea-water and securing a dry chamber, within which the various operations for building up the tube, and for pressing forward the bell as each ring of the tube is added, will be performed. There will always be 3 and generally 4 of these water-tight joints contained within the bell. A clear space between the end of the tube and the end or projecting part of the bell of 36 feet will be left as a chamber for the various operations. Within this chamber, powerful hydraulic presses, using the built and completed portion of the tube as a fulcrum, will, as each ring is completed, push forward the bell to a sufficient distance to admit the addition of another ring to the tube. The bell will slide over the water-tight joints described, one of which will be left behind as the bell is projected forward, leaving 3 always in operation against the sea. The weight of the bell and of the machinery within it will be a little in excess of the weight of water displaced, and therefore the only resistance to be overcome by the hydraulic presses when pushing forward the bell is the friction due to the slight difference in weight and the head or column of water pressing upon the sectional area of the bell against its forward motion. In like manner, the specific gravity of the tube will be a little in excess of the weight of water which it dis

places; and in order to obtain a firm footing upon the bottom of the sea, the tube will be weighted by a lining of brick in cement, and for further protection will be tied to the ground by screw piles, which will pass through stuffing-boxes in the bottom of the tube. These piles will, during the construction of the tube within the bell-chamber, be introduced in the annular space between the outside of the tube and the inside of the bell, and will be screwed into the ground as they are left behind by the progression of the bell. The hydraulic presses, and the other hydraulic machinery which will be employed for lifting and fixing the various segments of the tube, will be supplied with the power required for working them from accumulators on shore, on Sir William Armstrong's system, and the supply of fresh air required for the sustenance of the workmen employed within the bell and within the tube will be insured also by steam power on shore. As the tube is completed, the rails will be laid within it for the trains of wagons to be employed in bringing up segments of the rings as they may be required for the construction of the tube, and for taking back the waste water from the hydraulic presses, or any water from leakage during the construction. The tube will be formed of rings of 10 feet in length, each ring consisting of 6 segments, all precisely alike, turned and faced at the flanges or joints, and fitted together on shore previously to being taken into the bell, so that on their arrival the segments may, with perfect certainty and precision, be attached to each other. The tube when laid will be secure from all dangers arising from anchors, or wrecks, or submarine currents. The building of the tube will be commenced on dry land above the level of the sea, and will be gradually submerged as the tube lengthens. The first half mile will test the feasibility of construction, for that will have to be built both above and under water. When once fairly under water, the progress should be rapid, and it is estimated that the whole undertaking may be easily completed in 5 years. The precise line to be taken will probably be between a point in close proximity to Dover, and a point in close proximity to Cape Grisnez, on the French coast, where the sea bed on this line appears to be the most uniform in level, and, while free from hard rocks and broken ground, to consist of coarse sand, gravel, and clay. The average depth of water is about 110 feet, the maximum about 200 feet. On the line suggested the water increases in depth on both sides more rapidly than elsewhere, although in no instance will the gradient be more than about one in 100. The tube, when completed, will occupy about 16 feet in depth above the present bottom of the sea. to the point on each shore at which the depth of water above the depth of the tube would reach, say 30 feet at low water, an open pier, or other protection, would have to be constructed for the purpose of pointing out its position, and of preventing vessels striking against the tube. The tube at each end would gradually emerge from the water, and on arriving above the level of the sea would be connected with the existing railway systems. The distance across the Channel on the line chosen is about 22 miles.

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