This technical work provides a detailed account of the construction of the Harlem River Tubes, an important part of the New York City subway system. Written by engineer Howard Babcock Gates, the book covers topics such as tunneling, excavation, and the use of compressed air in construction. This volume will be of interest to anyone studying the history of engineering or urban development in the United States. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.