D. H. MAHAN, LL.D.,

LATE PROFESSOR OF CIVIL ENGINEERING AT WEST POINT, N. X.

REVISED AND EDITED, WITH ADDITIONS AND NEW PLATES,

BY DE VOLSON WOOD,

PROFESSOR OF MATHEMATICS AND MECHANICS IN STEVENS' INSTITUTE OF TECHNOLOG:
(FORMERLY PROFESSOR OF CIVIL ENGINEERING IN THE UNIVERSITY OF MICHI-
GAN); AUTHOR OF A TREATISE ON THE RESISTANCE OF MATERIALS;
TREATISE ON BRIDGES AND ROOFS, ETC.

NEW EDITION,

WITH CHAPTER ON RIVER IMPROVEMENTS.

BY F. A. MAHAN,

CAPT. ENGINEER CORPS, U.S.A.

NEW YORK:

JOHN WILEY & SONS,

15 ASTOR PLACE.

1880.

ENTERED, according to Act of Congress, in the year: 573. he

JOHN WILEY,

In the Office of the Librarian of Congress, at Washington, D. Q.

THE works of the late Professor Mahan are too well and too favorably known to need special comment from the present Editor.

The first edition of his work on Civil Engineering appeared when engineering as a learned profession was scarcely recognized in this country, and when but a very limited amount of instruction upon the science which pertains to it was given in our schools. Descriptions of processes and of works executed were the essential means of giving the information which was needed by the engineer. This determined the essential characteristic of his work, which is descriptive.

More recently, numerous schools have been established, which are intended to give thorough instruction in the science of engineering, and in which the courses of instruction are largely filled with mathematical analysis. But analysis alone, however important, can never take the place of descriptive matter. Every successful structure serves as a guide in the construction of all future similar works. Thus the experience of one may become the wisdom of many.

Before his untimely death, Pr fessor Mahan had prepared

a thorough revision of this work, and about one-third of it had passed through the press when the present Editor took charge of it.

I have endeavored to do full justice to the original author by preserving the essential character of the work, and retain ing nearly all the matter which he had prepared; still, I have omitted a few paragraphs which were deemed non-essential, and condensed others. I have also added considerable new matter, which is scattered throughout that portion of the work which I have had in charge. I trust that my labors have added to the value of the work.

DE V. W.

HOBOXEN Aug., 1978.