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A TREATISE ON DREDGES AND DREDGING 



\Vith semi-sea-going dredges, navigating in waters which :uv 

 usually quiet and calm, the propelling apparatus is of secondary 

 importance. This consists of a single screw located at the stem in the 

 ladder pit, when the stern in navigation becomes the bow in dredging. 

 Fig. 18 shows the semi-sea-going ladder dredge " Cadiz " built l>y 

 the H. Satre Fils Aine et Cie. for the harbor of Cadiz, Spain, in which 

 'the propeller is located in the pit. The propelling apparatus may 

 consist also of a single paddle-wheel located in the ladder pit. 



It is not possible to use two side wheels on account of the chutes 

 for the dredged materials. In such a case the walls of the pit are 

 greatly extended as indicated in Fig. 19, which represents one of 

 these dredges built by the H. Satre et Cie. and used in the canal 

 between the Marne and Rhine rivers. The propelling apparatus 

 may consist also of a sprocket wheel of large dimensions located 

 at the stern. In revolving, the wheel will engage continuously 

 the bed of the river, thus causing the forward motion of the dredge. 



FIG. 19. Dredge for the Marne Canal. 



This method of propulsion was ordered by the Department of Fonts 

 at Chaussees in France for dredges to be used in the improvement 

 of the Rhdne River, one of which is shown in Fig. 'JO. 



