WANGANUI RAILWAY BRIDGE.

New Zealand Times, Volume XXIX, Issue 4134, 20 June 1874, Page 3

WANGANUI RAILWAY BRIDGE.

(From the Chronicle, Juno 17.) A most substantial piece of work is about to bo undertaken in the shape of a railway bridge across the Wanganui, tenders for the erection of which have already been sent in to the department at Wellington. The site of the bridge will be some two miles above the present one. It is designed on Howe’s trass principle, and the plans show a composite structure of wood and iron, similar to many of the railway bridges built or about to be built by the General Government in different parts of New Zealand, which all proceed from a common design furnished by the Public Works Department, The bridge itself, without the approaches, will measure COO feet in length, the distance being covered by five spans of 120 feet each. There will bo four piers, each consisting of two cast iron cylinders, seven feet in diameter and seventy feet long. These cylinders will be sunk in the ground to a considerable distance ; those belonging to the two northernmost piers to a depth of 23 feet, and on the other side, to a depth of 20 foot. They will bo filled with concrete, on the top of which a

packing of totara will be placed, for the superstructure to rest upon. The cylinders -will contain 321 tons of iron altogether. The superstructure will be partly composed of wood and partly of iron, A lower beam of malleable iron will be covered by an upper one of totara and jarrah ; and the permanent way will be supported by iron cross bands with totara or jarrah stringers. Each span will be a separate and distinct structure from the rest ; one end of it being fixed and the other resting upon rollers ; provision being made by this ingenious contrivance for the expansion of the iron by temperature, and the effects of a 1 passing train. The width of the bridge, over all, will be 25 feet, and of the roadway, 14 feet, sufficient to allow of one line of rails being laid down. The roadway is 32 feet above high water and 24 feet above flood mark. The approaches will be of a massive description, more especially the northern one. This is iuteuded to consist of a concrete abutment 132 feet in length on the ground surface, and carried down 13 feet beneath low water mark, until the solid is reached, where it will rest upon 110 piles each 33 feet long. It will have a rubble facing below the water. The southern approach will he 220 feet long, but of much smaller dimensions otherwise. It will also be formed of concrete, and rest upon 44 piles of either totara, rimu, or black birch, the contractor being allowed his choice. The total length of bridge and approaches will thus be 952 feet, and if the contractor executes his task with as much skill as has been displayed in the preparation of the designs, a bridge will be placed over the Wanganui river creditable to the Public Works Department and of an enduring benefit to the inhabitants of the West Coast.