INTRODUCTION. THE greater part-of foundation worli is of an ordinary character. And while difficult foundations have been quite fully treated by engineering writers, ordinary ones have too often. been-passed over with mere mention, or treated in such a general way that the information proves of little value in actual practice. Many valuable examples of work of this character have been described in current engineering literature, and it is hoped that by bringing them together a real service will be rendered the profession, as well as much valuable time be saved for considering other and equally important. problems. The history of the coffer-dam process would seem to indicate that engineers of-nearly a century ago gave more consideration to the smaller problems than the engineer of to-day, who has apparently passed to the consideration of the larger and of course more interesting ones. That this is deplorable, is proven by the many cases where money has been wasted in the after effort to make good the mistakes that have become apparent where cheap construction of coffer-dams has been resorted to. The saving in original cost, as between an indefensible method and a defensible one, is often so small as to seem absurd when it. has become necessary to make large expehditures to rectify the errors. . Errors of judgment-are more easily excusable with regard to foundations than with any other class of construction, but where definite limits can be set, economy will result by keeping as closely as possible-within them. ix X INTRODUCTION Reference is made in the following pages to the splendid construction of foundations by the Romans, where they could be built outside the water. The Pont du Gard, illustrated in the frontispiece, is the most notable example of this extant...