THE GREEN WAY BREAK WATER.

New Zealand Herald, Volume XXII, Issue 7402, 10 August 1885, Page 6

THE GREEN WAY BREAK WATER.

Our readers may remember that several years ago an Indian Judge, Mr. E. C. Greenway Thomas, visited this province, and took considerable interest in the Maoris and their system of land tenure. Since he left this part of the Empire, he has paid much attention to the need of new harbours of refuge for such a sea-going people as the British are. The cost of breakwaters or other harbour works of the usual solid construction, either masonry or conorete, is so expensive that few such can be built, on account of their enormous cost. As instances of this, may be mentioned the Now Plymouth breakwater and the Oamara and Timaru harbour works in our own colony. In each placo a harbour has boon constructed, or is in courso of construction, where naturo never intended one to be, and after the enormous cost which oach will entail, it yet has to be proved whether they will remain, or be destroyed by some exceptionally severe storm. Time alone can settle such a question. In many parts of the world heavy structures have boen erected for harbour purposes in very exposed places, and tho results in some instances are such that most thinking people will suspend their judgment before expressiug an opinion as to the permanency or otherwise of the expensive works undertaken in some plac-s in New Zealand. But the invention of Judge Thomas, which he has patented under the name of the Greenway breakwater," is a plan whioh would be admirably adapted for providing shelter in such exposed places as those named. Tho shelter provided would not only be effectual, but it would also be cheap, and is of such a oharacter that repairs could easily be effected, or even the whole plan of harbour protection might be changed in a few days if the one first designed and carried out did not afford the required protection. This is a great point in favour of Mr. Thomas' invention ; and the method he has adopted, while it affords protection for the shipping which seek its shelter, does not interrupt the natural flow of the water, and thus the silting up which follows the erection of solid masonry works is prevented. This also is a point deserving of much consideration on a coast where there is shifting sand, or a shingle bed subject to the action of the inrolliug waves. The natural source of tha ebb and flow of the tide is not chocked, while the shelter provided within the enclosure is sufficient for all practical purposes that a breakwater is required for. Indeed, by the use of Mr. Thomas' invention, a shelter for shipping may bo provided at any suitable place along the coast where the depth of water is not ton great, even where there may be no natural harbour, good shelter for shipping could be provided at a very reasonable cost. The Greenway Breakwater, or Turnwater, is constructed by an ingenious use of a number of iron buoys. These are made of a triangular shape, ten feet on each side, and the main body ten feet deep, the upper part tapering from the shoulder to a tine point at the top. These buoys are anchored when the breakwater is wanted, with a space the width of a buoy between each. They are anchored so as to present one of the sharp corners to the exposed front. The sides of each buoy between the angles is not flat, but concave, so that when a number of buoys are anchored in line in an exposed front, the waves rush madly on to the sharp edges, and the body of water meeting the concave sides is deflected in its course, and a slight rotary motion is thus given to it so that the wave motion is thrown from each buoy to a point and rushes back to meet the next incoming wave, and thus the force of the two waves is neutralised by contact with each other. The lino of buoys thus anchored along the exposed front is elastic to the wave motion at all times, but it is when the storm is fiercest that the full advantage of the back current established by the concave sides of the buoys Is most completely felt,. This line of buoys'may be single or double, and while the wildest confusion may reign outside this lino of protection, inside will be found calm and seoare anchorage in all weathers. The curved sides of the buoys is a happy idea, as by it the impact- from the wave motion is avoided, and the on-rush of the water merely deflected in its course, and made to roll back with scarcely diminished velocity upon the next wave. These opposing currents meet outside the line of buoys, and thus spend their force in fierce mutual contact.

The buoys are of course made of iron, and can be easily and readily repaired when necessary. As they are sunk in the water ten feet, and the depth of water in motion during a severe storm seldem exceeds from 15 to 20 feet, a breakwater of these buoys, especially if there is a double line, may be regarded as ample in the severest weather upon the most exposed coast to provide a safe and cheap shelter for shipping of all sizes. It may also be affirmed that the protection thus afforded is a oheap one, as it is stated that the average cost of a single line of buoys is £30,000 per mile, or £20 a yard. If the buoys are brought to the place made it is stated that they can be placed - in position at the rate of about 100 yards a day. It will thus be seen from the nature of the protection afforded that sheltered anchorages and harbours might be found by the Greenway breakwater in the depth of water which would make the construction of a solid wall almost impossible. The deepest part of the Admirality pier at Dover cost at the rate of about £2,000,000 per mile, while by the use of Mr. Thomas'ingenious invention, effectual protection might have been afforded to the shipping at a mere fraction of that cost. There are some printed documents on this subject, which may be perused at our publishing office by those interested in the matter. Mr. Thomas also patented an invention which he calls the " Electric Light Buoy," by which an electric light is produced by the motion of the waves, and which is said to act automatically.