CORRESPONDENCE.

Taranaki Daily News, 18 July 1921, Page 2

CORRESPONDENCE.

BREAKWATER EXTENSION, (To .the Editor.) Sir,—ln your issue of 15th irist., appears what is therein termed a new suggestion for extending the breakwater by means of hollow concrete blocks. This is not new by any means. As I write I have before me a double page picture from the Illustrated London News of January. 26, 1918, showing the size of hollow concrete blocks being used in the construction of the new breakwater at Valparaiso. The heading over the picture is “eight and a half thousand tons of stone afloat! a great British engineering feat/’ These are enormous hollow concrete blocks which weigh when In position 13,370 tons and when afloat 8,560 tons. They measure 65 feet 7 inches long by 52 feet &in wide and 49 feet 5 inches high. I take it that these blocks are built on ways like a ship, and when quite dry launched and towed out to the position required and then sunk. Whether they are then filled with gravel or sand I don’t know, or perhaps the action of the sea does this work. My picture shows a tug towing out one of these immense blocks to a point where it is to be sunk, and in passing a full rigged ship the top of the dock stands as high out of the water as the skip’s lower topsail yard. I don’t know Valparaiso, but possibly owing to the depth of, water and Weight of the heavy sea it jS necessary to have such large blocks. Would it not be well worth trying the same method of construction at Motorua by putting down aay a small section of the proposed extension? I don’t suggest that we put down 8500 ton blocks, but I do think the question of putting down hollow blocks of a few hundred tons each should be carefully gone into. If something of the kind could be done the saving of material, time and labor should be considerable.—l am, etc, A.B. New Plymouth, July 15.,