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SAMUEL DOWNING, M. A.,

PRoFESSOR OF CIVIL ENGINEERING IN THE UNIVERSITY OF DUBLIN.

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INTRODUCTION.

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, " Traite 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 FOurcq—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 magnitude, which have, when completed, been found to fulfil perfectly their intended objects, and consequently it may be considered as based on an experience the most reliable, and, of all others, the most valuable to the civil engineer.

Throughout this work, the only dimension used is the foot and the cubic foot. We have in English works on Hydraulics a great variety of units: the gallon, the cubic foot, the ton, the cubic yard; and for length, the yard, foot, and inch. As soon as the student has become familiar with the value of the inches in a foot expressed decimally, it is hoped that this arrangement will be found useful. Of the eleven decimal fractions for the inches in a foot, five are well known, and the rest may be readily remembered:—

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The Author takes this opportunity of returning thanks to the Board, for the liberality they have shown in defraying the greater part of the expenses of this Work.

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