PREFACE.

In presenting to the public a new technical work, it is the custom to offer some sort of apology for its appearance; hence the author of this treatise, in order not to be considered peculiar, feels it incumbent upon him to do likewise. Moreover, there is in this case a good reason for beginning his book with an apology, because of his audacity in imposing upon the good nature of the engineering profession by asking its members to read still another work upon the already overwritten subject of bridges. If he could do so, the author would here plead primum tempus; but this is by no means his first offence. Perhaps, though, the fact that it is twelve years since the appearance of his last book (pamphlets, of course, excepted) will be considered by his critics as a "mitigating circumstance" in this case.

But, to speak seriously, if this work were a mere rehash of other books, or if it dealt with the same old, worn-out subjects, the author would not presume to present it to the engineering profession; but, on the contrary, in writing it he has endeavored to make the contents as original as possible, and to treat essentially of the fundamental principles of bridge-designing and their application. It will be noticed throughout the book that quotations from other works on bridges are "conspicuous by their absence," and that the author has drawn almost entirely upon his own professional practice for examples to illustrate his text. For the latter no apology is required, because his own designs (as far as the process of development has permitted) have naturally been made in conformity with the principles which he herein offers as a guide to bridge-designing; and they are therefore more appropriate as illustrations than the designs of others.

v.