Ban goc (Tiếng Anh)

PREFATORY NOTE 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 principl