So much has been written on this subject that it is next to impossible
to be wholly original, and no claim of that nature is preferred. It is
simply an arrangement of ideas, gleaned from the various works of
standard authorities, and modified by the author's practice, embodied
in book form. To give a correct list of all the books consulted would
be simply impossible;--but it is well to state that the Hand-book of
Railroad Construction, by Prof. G.L. Vose, under whom the author
served as an Engineer, has been used as authority in many cases where
there has been a difference of opinions among other authors. Some
parts have been quoted entirely; but due credit has been given, it is
believed, wherever such is the case.

It is not claimed that this little work covers the whole ground, but
it is intended to describe, and explain thoroughly, three or four of
the more prominent styles of Truss, leaving the other forms of Wooden
Bridges to a subsequent volume.

Abutments and Piers, as well as Box and Arch Culverts, belonging more
properly to masonry, will be treated of hereafter under that head.

Iron Bridges form a distinct class, and may be mentioned separately at
some future period.

If this small volume should lead the student of Engineering to examine
carefully the best Bridges of modern practice, and study the larger
scientific works on this art, the author will feel satisfied that his
efforts have not been entirely in vain.

_Cambridge, February 23, 1874._