As respects the preparation of the following memoirs, the Author's principal task has consisted in selecting and arranging the materials so liberally placed at his disposal by gentlemen for the most part personally acquainted with the subjects of them, and but for whose assistance the book could not have been written. The materials for the biography of Henry Maudslay, for instance, have been partly supplied by the late Mr. Joshua Field, F.R.S. (his partner), but principally by Mr. James Nasmyth, C.E., his distinguished pupil. In like manner Mr. John Penn, C.E., has supplied the chief materials for the memoir of Joseph Clement, assisted by Mr. Wilkinson, Clement's nephew. The Author has also had the valuable assistance of Mr. William Fairbairn, F.R.S., Mr. J. O. March, tool manufacturer (Mayor of Leeds), Mr. Richard Roberts, C.E., Mr. Henry Maudslay, C.E., and Mr. J. Kitson, Jun., iron manufacturer, Leeds, in the preparation of the other memoirs of mechanical engineers included in this volume. The materials for the memoirs of the early iron-workers have in like manner been obtained for the most part from original sources; those of the Darbys and Reynoldses from Mr. Dickinson of Coalbrookdale, Mr. William Reynolds of Coed-du, and Mr. William G. Norris of the former place, as well as from Mr. Anstice of Madeley Wood, who has kindly supplied the original records of the firm. The substance of the biography of Benjamin Huntsman, the inventor of cast-steel, has been furnished by his lineal representatives; and the facts embodied in the memoirs of Henry Cort and David Mushet have been supplied by the sons of those inventors. To Mr. Anderson Kirkwood of Glasgow the Author is indebted for the memoir of James Beaumont Neilson, inventor of the hot blast; and to Mr. Ralph Moore, Inspector of Mines in Scotland, for various information relative to the progress of the Scotch iron manufacture. The memoirs of Dud Dudley and Andrew Yarranton are almost the only ones of the series in preparing which material assistance has been derived from books; but these have been largely illustrated by facts contained in original documents preserved in the State Paper Office, the careful examination of which has been conducted by Mr. W. Walker Wilkins. It will thus be observed that most of the information embodied in this volume, more especially that relating to the inventors of tools and machines, has heretofore existed only in the memories of the eminent mechanical engineers from whom it has been collected. The estimable Joshua Field has died since the date at which he communicated his recollections; and in a few more years many of the facts which have been caught and are here placed on record would, probably, in the ordinary course of things, have passed into oblivion. As it is, the Author feels that there are many gaps yet to be filled up; but the field of Industrial Biography is a wide one, and is open to all who will labour in it. London, October, 1863.