CONTENTS. Malleable Iron-its Manufacture into Plates and Bars of different Sec- tions-The application of Iron Plates in the formation of Steam Boilers-and of Plates and Bars in building Ships, Caissons, &c. 11-21 First Constructions of Wrought-Iron Plate Girders-Mr. Fairbairn's Patent Wrought-Iron Tubular Girders-Their application to Bridge-building- Bridge on the line of the Blackburn and Bolton Railway-Bridges of the Liverpool Landing Stage - Great Bridge erected by Messrs. Fairbairn and Sons, on the line of the Manchester, Sheffield, and Lin- Proceedings, and Engineers' Reports upon the Communication between London and Dublin-Iron Bridges proposed by Mr. Rennie in 1802- Mr. Robert Stephenson's Design for Cast-Iron Arched Bridges, and selection of Site over the Britannia Rock-Admiralty Opposition, and General Principles which distinguish Girder Bridges from Arched Bridges -Mr. Fairbairn's Experiments and Report on Tubular Girders-Mr. Hodgkinson's Experiments and Report-Mr. Stephenson's Report 62-92 Description of the BRITANNIA BRIDGE The Masonry- Britannia Tower-Anglesea and Caernarvon Towers and Abutments-Arrange- ments for constructing the Tubes-Main Tubes and Land Tubes— Description of their Construction-Scaffolding and Staging-Arrange- ments for floating the Tubes-The Pontoons-Raising the Main Tubes- The Hydraulic Press - Connecting the Tubes in the Towers - The INTRODUCTION. ENGINEERING Works being usually of a public character, naturally excite a general interest throughout the community, the extent of which feeling is commonly commensurate with the novelty, the magnitude, and the utility of the performance. Thus, a railway, a harbour, a lighthouse, a dock, or a bridge, regarded as subservient to public convenience, is watched with public anxiety, and its completion becomes an occasion of public gratulation. Such a work is therefore a peculiarly suitable subject for one of a series of Rudimentary Volumes, dedicated, in their several features of style, size, and price, to the use of a largely-extended circle of readers and students. And it must be admitted by all that the works which form the main subjects of the following pages have claims of nearly unprecedented amount upon our attention, being new, great, and useful in a pre-eminent degree. The application of wrought iron to the purpose of bridgebuilding truly constitutes a new branch of the art, and is, as already proved, susceptible of modifications of form and construction, far more efficient than those of the cast metal. A perfectly horizontal and rigid roadway or railway, 460 feet in length, and having only 3 feet of depth below it, could not be obtained by any other known arrangement of parts than that herein illustrated; and with these successful examples before us, the task of future designing is facilitated to an incalculable extent. For smaller spans the depth of construction may be still further reduced, as shown in the splendid bridge over the Trent, described in this volume; and for the particulars of which we take the pleasure of expressing our obligation to Messrs. Fairbairn and Sons, who have also rendered us much other valuable aid throughout this little work, and thus furnished another proof of their known liberality in acquainting others with the useful and often costly results of their own extended experience. It is seldom that the invention of works of new design and skilful mechanical arrangement is due entirely to one mind, any more than their construction is due to one pair of hands : hence great difficulty arises in assigning to each contributor his fair share of merit in their production. It must, however, be admitted, that to Mr. Robert Stephenson alone we are in this instance indebted for the original suggestion; and, with this admission, we have endeavoured to avoid any attempt to judge of the precise claims of the two eminent men whose joint labours have produced the Conway and the Britannia Tubular Bridges. That these great works owe their design and construction to these joint labours is clearly evident, and, we respectfully submit, amply sufficient to justify the record of the two names of ROBERT STEPHENSON and WILLIAM FAIRBAIRN in an honourable and enduring association. In order to give a glimpse at the experience which had been had in Iron Bridge-building prior to the use of the malleable material, and to show the defects which this was designed to obviate, a brief sketch of the history of Iron Bridges is prefixed. This is followed by a notice of former applications of malleable iron, with the view of bringing up the sketch to the period at which tubular girders were first used. The description of the works of Telford upon the Holyhead Road is introduced on account of the generally interesting character of those works, and the absence of any account of them within the reach of ordinary readers. While exalting the names and works of our own time, we can readily afford to acknowledge the claims of those of a preceding age. JAN. 1, 1850. |
