116 A TREATISE ON DREDGES AND DREDGING 



raised, and the dredge proceeds to sea, where it discharges its load 

 by performing the series of operations previously described. 



The fittings of the dredge are unusually complete throughout, 

 and a particular attempt has been made to provide comfortable 

 quarters for the officers and crew. These quarters, together with 

 the messrooms, pantries, etc., are located above the main deck, 

 as shown by the drawings, which also show in sufficient detail the 

 above-deck structure and rigging. 



The following description of a hydraulic dredge with two suction 

 pipes and a central hopper is taken from Engineering, November 

 22, 1901. 



The lower reach of the Seine, from Rouen to the open sea, had, 

 until recently, been practically unused for maritime service, 

 although it might have been made a first-class channel for commercial 

 purposes. Navigation, as far as Rouen, was carried out under 

 very great difficulties, owing to the varying nature of the water 

 discharge and the changing depths. Up till 1848, of the 78 miles 

 which separate Rouen from the sea, 37, at least, formed an estuary 

 of exceedingly great width, useless in the point of view of navigation, 

 the fairway being a shallow and very changeable one, in the midst 

 of shifting sandbanks and mud. In the period from 1848 to 1866 a 

 series of longitudinal dykes were built on both banks, the total devel- 

 oped length of which rapidly extended to over 40 miles; these 

 gave good results in the sense that they deepened the channel at 

 many places. From 1866 to 1885 no new work was carried out, 

 and the maintenance in good state of repair of the dykes previously 

 built with unsuitable material was very laborious. Since 1885 

 attempts have been made to improve the conditions of navigation 

 up-stream from the Risle River, and the conditions of the estuary 

 proper. The object is to regulate the distance between the opposite 

 banks in such a way that the body of water available is the largest 

 possible, dredging being resorted to in order to improve the flow 

 and deepen the channel. In 1895 a powerful bucket dredge was 

 put in service; this was found very efficient, in that it easily reduced 

 to 3 ft. under the zero of the charts, beds that were formerly above 

 zero. As soon, however, as an experimental suction dredge had 

 been tried and found to give excellent results, the Seine Board of 

 Works ordered three powerful ones of this system from the Sorii'u' 

 des Anciens Etablissements Satre, of Lyons, Aries, and Rouen. 



There being very often rough weather on the Lower Seine, 



