A NEW BREAKWATER.

New Zealand Times, Volume XXXIII, Issue 5411, 31 July 1878, Page 3

A NEW BREAKWATER.

- - Mr, Thomas Hirst, a well-known settler in the provincial district oE Taranaki,' has invented a breakwater which is designed on an entirely now principle—one that to the lay mind appears to possess great merit. The models have been submitted to Sir John Ooodo, to many local engineers and others, and the verdict has been generally in favor of Mr. Hirst’s idea. Sir John Goode checked the calculations as to cost, and agreed that to erect a breakwater on the plan proposed would be cheaper than to build a wall-faced pier. Mr. Hirst’s plan has these main features:—Circular cones of concrete, placed in two rows, connected with others at the base, with open-work iron girders connecting them at the top. It is proposed to have each tower of the following dimensions 52ft. in diameter at the base, 16ft. in diameter at the top, and about 22 ft. high. The material used will bo concrete, in blocks, and before placing these in position there will bo lowered into the water a skeleton iron frame, weighing 13 tons, supporting tho towey ■ to whibh tho girders are fitted. Tho blocks will have on the outside notches, into which an iron bar will run, so as to keep them in position, and the centre, which will be like a circular well, will be filled up with concrete. Tho tower will be circular, and will bo in 10 steps of 2ft. each. These towers will he placed so that tho connecting girders will represent a zig-zag, and by this means great strength will be secured to them, as the ends will receive support not only from tho pillars but from two other girders. Midway along each there will be iron stays, springing from a concrete bed, It is intended that the circular cones shall, not roach more than 2ft. above low-water mark, and thus they will hot be subjected to tho force of tho swell, and tho sea will break against tho iron girders, and bo so split' by them that tho water inshore will bo calnp’ The girders will bo 12ft. high, 4{t, wide, and about 48ft. in length, Tho iron used is round, generally

2Jin; ! ‘diameter,'' and it'is thought that this size will offer so little resistance to the sea that the shock will imfc.be very severe. lu the‘model Mr. Hirst has with him, one givder is represented aimvlo of wire rope, so that it will have coiisiderabb elasticity, and the other is niade perfectly rigid. Opinions as to which would be the stronger differ, some holding; that the girder which would give to the,, shock would outlast the other. It is held by the inventor that these girders, which appear like gigpnfcic trellis work, will so thoroughly break the force of the sea chat vessels will be able to lie in smooth water at an ordinary wharf inside the breakwater. iThe object Mr. Hirst has- kept in view is, while avoiding the fierce shock of the gigantic waves that roll in on au exposed \shora ■ during heavy weather, to so divide the rollers that comparatively still water will be secured in shore,.of ,them. The two doubts which strike oiiq arethe ques-. fcion; of cost and the strength of the girders. As to the/former, Mr. Hirst- has made moat careful calculations, which have been verified by Sic John Goode ; : and as to the latter, the opihion.of, experts is that the iron will stand securely, and yet do all it is intended to accomplish, : The effect of sea water on iron is feared by some; but-of late compositions have been discovered which will sufficiently protect the iron.'' A tower and girder will cost £4OOO. In places where the sea is not heavy a single line of. piers would suffice/but the two rows would be recommended in most cases. Mr. Hirst has his models at Barrett’s Hotel, and will be willing-to explain.them to anyone who takes an'interest in such matters. Should 1 the inventor be correct in his theory, the breakwater would be of enormous value in thii - for it would be easily constructed at a cqst considerably less than such a work ?s the Oamaru pier. ’ v ' ! : '• ;