This volume is not intended to be a complete record of inventive genius and mechanical progress in the United States.A bare catalogue of notable American inventions in the nineteenth century alone could not be compressed into these pages.Nor is it any part of the purpose of this book to trespass on the ground of the many mechanical works and encyclopedias which give technical descriptions and explain in detail the principle of every invention.All this book seeks to do is to outline the personalities of some of the outstanding American inventors and indicate the significance of their achievements.

Acknowledgments are due the Editor of the Series and to members of the staff of the Yale University Press particularly, Miss Constance Lindsay Skinner, Mr.Arthur Edwin Krows, and Miss Frances Hart--without whose intelligent assistance the book could not have been completed in time to take its place in the Series.

H.T.

COLLEGE OF THE CITY OF NEW YORK, May 10, 1921.