CHEAP BRIDGES.

Nelson Evening Mail, Volume V, Issue 48, 26 February 1870, Page 2

CHEAP BRIDGES.

Mr. Doyne, an engineer of eminence, planned n bridge to span the Rakaia, a large and rapid river in Canterbury, which would have cost £300,000 — a sum beyond the Provincial means. Mr. White, a plain amateur engineer, who had already conj structed bridges with success over the ! treacherous Waimakariri, iv spite of all prophecies of the c'e ' regulars" to the contrary, has erected a light and cheap structure across the Rakaia, which is expected to answer admirably. A Canterbury paper says that should this bridge stand as well as Mr. White's other bridges, he will have established his fame as the first of New Zealand engineers. The following is a description of the structure: — " In casting about for some inexpensive method of securing the scaffolding necessary for pile-engines, the contractor hifc upon the plan" of driving tubes, such as are now so extensively used about Christchurch in artesian wells — gaspiping iv fact — and finding it succeed well the idea grew ; so, extending his operations, he inserted them as piles from bank to bank, built upon them, and the result is, or shortly will be a bridge light, but strong, and which may be cheaply and expeditiously strengthened so as to bear any weight ever likely to test it. A tramway is laid, and there is ample room for foot traffic. It will be ready for use early in May next. There is nothing iv its appearance or construction to distinguish it from an ordinary very light trdssle bridge excepting the tubes, which are 16 feet long and 2^ inches in diameter, driven from 6 to 10 feet into the ground (large shingle and boulders) according to level; they are single, cix feet apart, boxed in, and three

of them support each capsil] . The tressling is of the lightest description, and is merely useful for . bracing only, as the weight of the bridge is supported entirely by the tubes. The bays are 20 feet each; the total length of bridge, 1280 yards, its width 12 feet. Of course, by doubling the tubes, Ly inserting intermediate tressles, and by trussing, !he bridge may stiffened to almost any extent, but it is supposed that it is sufficiently rigid and strong to meet its present requirements." _ ■ ,