WORLD'S BIG TUNNELS.

Shannon News, 7 January 1927, Page 4

WORLD'S BIG TUNNELS.

MILLIONS TO SAVE MINUTES. The opening of the new South London tube extension has provided Londoners and incidentally visitors to London with, a train ride through the longest tunnel in the world, a distance of fifteen miles. At the same time work has now started in earnest on what will be the biggest tunnel in the world —that is, the onewith the largest diameter. This is the tunnel under the River Mersey, from Liverpool to Birkenhead, which will have an inside width of 44 feet, as compared with the 27 feet of England’s next biggest tunnel, that under the Thames, between Rotherhithe and Stepney. The Liverpool-Birkenhead tunnel is expected to be completed in five years 1 time. It will carry two roads, one above the other, and the total cost will be in the neighbourhood of £5,000,000. The world’s longest railway tunnel excluding tube railways, is the Simplon, which pierces the Alps in Switzerland, and extends to Italy. It is a little over 12 miles in length. The longest in the British Empire is the recently opened Otira tunnel, in New Zealand, five and a quarter miles long. It pierces a range of mountains and took sixteen years to complete, the engineering difficulties encountered being of the most formidable character. Indeed at one period these were considered insurmountable, and the work was temporarily abandoned in despair. The Otira runs dead straight, ho that a person standing at one end can see right through to the other, though the daylight visible there is but a pin-hole. The United States of America, the land of many ' big things, possesses, curiously enought, comparatively few railway tunnels. This is explained, however, by the fact that American engineers prefer going round obstacles, whenever .possible, rather than boring through them. It is the exact reverse of the principle adopted by the pioneer promoters of the English railways. Indeed, so fascinated were some of these with the idea of tunnels, that in one instance they had a tunnel built purely and simply for its own sake. There was no tunnel on the plan of the route submitted by the engineer to the originators of the scheme, and he was asked to explain the omission. “There is no necessity whatever for a tunnel,” he said. we must have a tunnel!” insisted the promoters, and he was instructed to work one in somewhere. So he made a deviation that must have resulted in the additional expenditure of thousands of pounds in order to comply with instructions.