3/ THE ELEMENTS OF PRACTICAL HYDRAULICS: FOR THE USE OF STUDENTS IN ENGINEERING. BY SAMUEL DOWNING, LL. D., PROFESSOR OF CIVIL ENGINEERING IN THE UNIVERSITY OF DUBLIN. LONGMAN, BROWN, GREEN, LONGMANS, & ROBERTS. 6871 PREFACE. THE first edition of this work having been favourably received, the Author has very carefully revised the present, and added many Plates and Woodcuts, with several new Examples, of a character, it is hoped, adapted to train the mind of a student to the consideration of practical subjects in a practical point of view. The work is still, what it at the first was intended to be, a Text-book for students in the Engineering School of this University; as such, it deals with first principles, and their applications to practical construction, rather than giving a collection of Hydraulic Tables, or other matter chiefly useful to those engaged in the actual construction of Hydraulic works. The profession is now gradually assuming the form of separate and distinct specialities,—not the least interesting or important of which is Hydraulic Engineering; but in a wellarranged course of instruction for a University School of Engineering, the principles of all these branches of the profession should be taught to all the students, whatever their destination may be. It was to meet the want of a Text-book of this character, for Hydraulic Engineering, that this work was undertaken. The admirable experiments carried on at the Lowell Mills, Massachusets, U. S., by J. B. Francis, and published by him, have been quoted in this edition; and the results, as to the a discharge over weirs, have been compared with former experimenters, and exhibited in the form of diagrams. The Author desires to acknowledge, with many thanks, the liberality of the Board in assisting in the expense of this edition, contrary to their rule as to second editions; but this cannot be drawn into a precedent, as it was an acknowledgment, on their part, of the successful drainage of the College Park by the Author. In all cases of quotation, the names of the authors, whose works were made use of, have been fully given. To those who would wish to pursue the subject still further, the following works are recommended: Beardmore's Hydraulic Tables, 2nd edition. J. B. Francis, Lowell Experiments. Morin's Hydraulique, 2nd edition. PREFACE TO THE FIRST EDITION. THE following work is intended as a Text-book for the Students in the School of Engineering, Trinity College, Dublin, in that branch of their intended profession which has reference to Practical Hydraulics. The first two chapters are in a great degree a translation of D'Aubuisson's well-known work, "Traitè d'Hydraulique a l'usage des Ingenieurs," which has obtained extensive circulation on the Continent, as well as in England and America. The third chapter, relating to the flow of water in artificial channels, rivers, and pipes, is founded on the formula for the uniform motion of water, which is in very general use amongst English engineers, and possesses great advantages over that given by D'Aubuisson, in simplicity and facility of application. Indeed, we do not find that this more complex formula has obtained the full confidence of foreign engineers themselves. Thus M. Girard, who constructed the navigable channel intended to supply the street fountains of Paris with water derived from the river l'Ourcq-being in possession of all the necessary dimensions and data, except the rate of inclination of the surface in the longitudinal section-calculated this last by that more complicated formula of which we speak, but finally decided upon constructing the line with a fall nearly double that thus obtained (§ 120). The formula given in the third chapter has, moreover, served to determine the proportions and dimensions of many English works of the greatest |
