A great deal of this narrative is given in Mr. Edison's own language, from oral or written statements made in reply to questions addressed to him with the object of securing accuracy. A further large part is based upon the personal contributions of many loyal associates; and it is desired here to make grateful acknowledgment to such collaborators as Messrs. Samuel Insull, E. H. Johnson, F. R. Upton, R. N Dyer, S. B. Eaton, Francis Jehl, W. S. Andrews, W. J. Jenks, W. J. Hammer, F. J. Sprague, W. S. Mallory, and C. L. Clarke, and others, without whose aid the issuance of this book would indeed have been impossible. In particular, it is desired to acknowledge indebtedness to Mr. W. H. Meadowcroft not only for substantial aid in the literary part of the work, but for indefatigable effort to group, classify, and summarize the boundless material embodied in Edison's note-books and memorabilia of all kinds now kept at the Orange laboratory. Acknowledgment must also be made of the courtesy and assistance of Mrs. Edison, and especially of the loan of many interesting and rare photographs from her private collection. EDISON HIS LIFE AND INVENTIONS CHAPTER I THE AGE OF ELECTRICITY THE year 1847 marked a period of great territorial acquisition by the American people, with incalculable additions to their actual and potential wealth. By the rational compromise with England in the dispute over the Oregon region, President Polk had secured during 1846, for undisturbed settlement, three hundred thousand square miles of forest, fertile land, and fisheries, including the whole fair Columbia Valley. Our active "policy of the Pacific" dated from that hour. With swift and clinching succession came the melodramatic Mexican War, and February, 1848, saw another vast territory south of Oregon and west of the Rocky Mountains added by treaty to the United States. Thus in about eighteen months there had been pieced into the national domain for quick development and exploitation a region as large as the entire Union of Thirteen States at the close of the War of Independence. Moreover, within its boundaries was embraced all the great American gold-field, just on the eve of discovery, for Marshall had detected the shining particles in the mill-race at the foot of the Sierra Nevada nine days before Mexico signed away her rights in California and in all the vague, remote hinterland facing Cathayward.