A MARVELLOUS INVENTION. THE MURRAY MARINE STEADY FLOATING STEEL STRUCTURES A Revolution In Marine Engineering.

Progress, Volume II, Issue 8, 1 June 1907, Page 296

A MARVELLOUS INVENTION. THE MURRAY MARINE STEADY FLOATING STEEL STRUCTURES A Revolution In Marine Engineering.

When Christopher Columbus got off the egg incident, we all know what happened. The remark of a prominent American naval commander after hearing an explanation of the Murray system vividly recalls the story. "Been sticking up in front of us all our lives," said he '' and we have never seen it." By taking advantage of this thing which has ' been sticking up in front" of the whole world for centuries, the Scottish-American engineer Mr. Murray, claims that he has found out how to construct floating breakwaters, floating docks, coaling stations, lighthouses, wharves, forts, piers, every kind of construction known to the art of the marine engineer. He claims for them all perfect stability, as well as absolute safety in the most exposed situations ; a comparative cheapness of cost which is phenomenal and must be revolutionary; and unfailing success by reason of their immunity from all vicissitudes of the usual conflicts with the ocean. An American writei 'in the "Shipbuilder " describing this invention with force and clearness, says : — "A great basic principle has been discovered, namely, how to use the enormous water pressure at a depth in the ocean to provide static resistance that counteracts the possible oscillation due to wave action at the surface. By going deep enough down with buoyant steel caissons into the tranquil lower waters of the ocean that lie below the comparatively shallow surface stratum of wave disturbance, and by constructing these steel caissons so that they have at their base a wide-projecting and heavily weighted flange on which the superimposed water rests with ponderous weight, exerting at 32 feet below the surface a pressure of 2,160 pounds per square foot, or at 60 feet down a pressuie that exceeds two tons per square foot, Mr. Murray in effect secures a steady-floating foundation on which any superstructure, properly designed to minimise the wave blows, may be placed, be it lighthouse, breakwater or fortress. Such a foundation opposes the dead inertia of its own weight and the weight of the water resting upon it, to such a degree, that the wave blows above are powerless to disturb the equilibrium of the floating body as a whole. It is the familiar principle of the iceberg, but with important improvements on nature's plan, for there is only a light, buoyant air space at the top, nine-tenths of the weight is thrown to the base, and this base itself is widely projected beyond the central caisson, conditions all three of which mark gains towards stability. Thus we attain steady flotation, and can secure for a hundred and one uses decks or platforms rising from the surface of the sea that defy oscillation above because of the static resistance deeper down offered by their motionless and rigidly connected foundation."

A writer in a French magazine, who describes how he was sceptical at first and how he was easily converted into a strong believer, sums up thus : " The constructions are intended to resist all the perturbations which are produced on the surface of the ocean. It might seem at first sight that not only are these results impossible to attain, but that they are in contradiction with what has been admitted up to the present in oceanography. However. Mr. Murray has triumphed over the difficulties simply by submerging his floating structures

to a depth where the waters are absolutelystable and are not subjected to any action by the oscillation of the ocean surface. It is sufficient to understand the efficiency of the operation by recalling that the action of the billows on the superstructure is annulled by resistance of the deeply submerged portion of the floating structure. The deeper this submersion the greater the resistance, for the increase of depth itself increases the weight of the water, with the result that the lower structure suspended in this medium becomes more and more immobile. This theory is supported by numerous demonstrations." Take the case of a district wanting a harbour to which a railway can be made without

any of the expense incidental totheapproaches to a natural harbour, such as the tunnel at Lyttelton, for example. How such a case is provided for is shown in our illustration. There you have a breakwater out in the offing, and railwa}?- wharves floating out from the shore, and inside these structures there is perfectly calm water. Thanks to the basic principle, the breakwater and the other structures are doubly anchored. First, they are anchored naturally by the deep water, which so neutralises the shocks of the sea at the surface, that there is no "pull" on the structure : secondly, they are anchored artificially to the bottom, resisting the set of the currents, tidal and otherwise. In the second respect, the anchorage, these structures have the advantage over a floating ship, that they can use any number of anchors that may be desired. As a matter of fact, they are anchored by blocks of 50 tons (and more) of concrete : anchored to the solid rock, practically, the rock being of the engineer's making, being part of the construction. How long will they last ? As long as steel endures. This may be ensured by regular painting of the surface between wind and water, a process easily compassed in fine weather, after pumping out the water -ballast in the caissons. The heavy portion below gets crusted thickly with barnacles and such growths of the sea, which have the effect of preventing rust, consequently the more the barnacles the better for the life of the structure. When the trade demands extension there is no difficulty at all. All that the authorities have to do is to tow the breakwater further out and, building others, as many as may be required, to anchor them in the proper places. Of course they need not be continuous, for with a hundred feet of space between these the big waves, after passing, tumble harmlessly to pieces. Moreover they may be anchored in any formation : line or echelon, or any other, and at angles suitable for minimising the effect of tides and currents. Much of the current passes underneath, it must be borne in mind, and when there is travelling shinerle and sand — those bugbears of all modern breakwaters — they pass t by harmlessly in the ordinary way as if there

were no obstruction at all. Consequently the expense of dredging is avoided, the depths remain constant, there is no injury to the foreshore, and the spectacle so well known at Timaru, let us say, of the battle with the ocean maintained by daily train loads of rubble from the neighbouring quarry, run out and dumped into the sea. will never be seen. There is another great advantage : these floating structures are out of the reach of earthquakes, and even the tidal wave so often destructive to the solid walls of modem breakwaters may pass over their floating substitutes without doing them the least injury. Furthermore, these structures can be built in sheltered places and towed out in fine weather to their stations. As to the method of building : — the hollow lower flange is first of all built and put on the water, and then the upper caisson is added while the body is already afloat. Next, the first degree of submergence is secured by packing the flange with gravel, which has two and one-half times the density of water, and the structure can now be towed to a place where it is to be employed. Filling of the water-tight compartments with water, as a ship is loaded with cargo, sinks the structure to what may be termed the line of rigid flotation. It is then anchored and left to do its work. Bulkheads at frequent intervals provide against the danger of sinking by accidental ramming. Repairs can readily be effected, and painting as above described The basic principle gives many things besides breakwaters. Inter alia, it gives a lighthouse easily built in shelter, and anchored, not on the danger to be avoided, but at a comfortable distance out ; far enough to give warning before vessels get too near. It gives also bridges, with caissons at intervals that may easily be floated out of position to admit the passing of ships. Also, it provides forts with steady gun platforms, which can be disposed in, any numbers off the coast, each carrying more guns than a battleship, each having all round fire, and easily defended from torpedo and submarine attacks, by netting and structures of similar character, which not needing removal may be made of great strength. These forts too may be supplied with torpedoes, which aimed from the steady platform will be deadly. It is obvious too that requiring no seamen they will not interfere with the requirements of the navy. Besides being formidable and cheap for defence, these forts set free the ships of the navy for offensive operations and the protection of commerce. Our illustrations show the principle applied to bridges and forts. Structures may also be built to act on occasion as submarines, firing torpedoes ; and here you have the elements of a most deadly mine-field. Given the steady platform, there is literally

no end to the variety of useful structures that may be built upon it. Platforms for raising wrecks, coaling depots so designed that m rough weather there is always a lee side ; floating islands for observation purposes, floating hospitals, baths, wharves to any extent in existing harbours, hotels — these are among the many structures that may be enumerated as likely to be built on the stable platform so opportunely discovered. Such is the new invention which has been strongly described as the most important since

the introduction of steel into the industry of shipbuilding. Three eminent engineers in the United States have given it their warmest approval.* The world wants more lighthouses, breakwaters, dodLs ; more of all the aids to shipping, which, moreover, do not at present keep pace with the rapid development of shipbuilding, naval and mercantile. The invention offers to supply the demand at small cost comparatively and with a great increase of efficiency. Its utilisation has already been suggested for the harbours and approaches of the Panama Canal, with lighthouses far out at sea, and channels brilliantly lighted as the streets of a city, for the way in. There are suggestions too for the benefit of the Atlantic and Pacific coasts of America. There will no doubt also be an extension of suggestions to New Zealand, where the attempts to wrestle harbours from the ocean at various places have been given up for lack of means, and by

reason of the great uncertainties of such contests. On the whole we may, not improbably, look for enormous developments from the splendid discovery of Mr. Murray. *Note. — These are Messrs. Schuyler, Finkle and Haw good, Hydraulic and Marine Engineers, who have been connected with some of the laigest works in California They agree that the basic principle of Mr. Murray's invention is scientifically correct and practically feasible, that the cost of breakwaters, where the depth is les? than thirty feet, is substantially less for the Murray system ; that for greater depths there is no comparison, the cost of structures remaining the same, whereas the construction of solid work is, between thirty and sixty feet, largely increased, and beyond the last practically prohibitive , in fact the work is impossible.