Excerpt from Tunnel Shields and the Use of Compressed Air in Subaqueous Works Although the employment of a shield, with or without the aid of compressed air, in tunnelling operations is of English origin, and the length of tunnels so constructed in this country is many times greater than the total amount of similar work elsewhere, the subject is nowhere dealt with in Engineering text books written in English, except in Simms' Practical Tunnelling and Prelini and Hills' Tunnelling, which, however, touch only slightly on it as a part of the general history of tunnelling. Except for a few pages in these works, no account in English of shield-work exists save in the form of papers printed in the Proceeding of the Institution of Civil Engineers and some description of current works which have from time to time appeared in the technical journals. In French two books only on the subject have appeared: the very complete work by M. Legouez, L' Kmploi du Boueiier dans la Construction des Souterrains, and M. Philippe's Le Boudier, which gives some interesting information on recent French tunnel works. The Author hopes, therefore, that a history of recent developments in shield-work may be found of some use to his profenuona) brethren, if only by collecting in one volume a mass of information hitherto scattered through many publications, and consequently difficult and troublesome of access. He has treated as briefly as possible the early records of the shields, and of compressed air working, holding, indeed, that only with Mr. Greathead and his Tower subway shield the history of practical tunnelling by shield really commences, but of the developments witnessed since he has endeavoured to present as clear a record as the limit* of one volume will permit. Of the Great head shield work, the "assisted shield" method of tunnelling, and the various subaqueous tunnels recently built in and around London, he may claim to write from personal knowledge, supplemented by information generously placed at his disposal by the Engineers engaged in the various undertakings described. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.