The MS. papers which have been consulted for the purposes of the present volume are of an unusually complete and varied character. They consist of several thousand documents selected from the tons of business books and correspondence which had accumulated at Soho. The most important were selected and arranged by the late M. Robinson Boulton, Esq., who entertained the highest regard for his father's memory; and, from the character of the collection, the author inclines to the opinion that it must have been made with a view to the preparation and publication of a Life of Matthew Boulton,--which has not, however, until now been undertaken. Thus, among sundry papers endorsed “M. Boulton--Biographical Memoirs,” is found a MS. memoir in the handwriting of James Watt, entitled “Memorandum concerning Mr. Boulton, commencing with my first acquaintance with him,” and another of a similar character, by Mr. James Keir,--both written shortly after Mr. Boulton’s death. Another collection, endorsed “Familiarum Epistolæ et Selectæ, 1755 to 1808,” contains letters received from various distinguished personages in the course of Mr. Boulton’s long and interesting career. The number of original documents is indeed so large, that, but for a rigid exclusion of non-essential matter, these Lives must have expanded into several volumes, instead of being compressed into one. But the author believes labour to be well bestowed in practising the art of condensation, and that the interest of biography gains much by judicious rejection. What Watt said to Murdock as to the production of a machine, holds equally true as to the production of a book,--“It is a great thing,” said Watt, “to know what to do without.” Besides the memoirs of Boulton and Watt, which occupy the principal places in the following volume, it will also be found to contain memoirs of the other inventors who have at various times laboured at the invention and application of the steam-engine,--of the Marquis of Worcester, Dionysius Papin, Thomas Savery, and Thomas Newcomen. The author has also been enabled to gather from the Boulton papers a memoir of William Murdock, which probably contains all that is likely to be collected respecting that excellent and most ingenious mechanic.