CHAPTER XII 



SEMI-SEA-GOING STATIONARY AND HIGH-TOWER LADDER 



DREDGES 



THE ladder dredges designed to work on rivers, canals, or within 

 well protected harbors are built of different types. For sake of clas- 

 sification these various dredges can be grouped into semi-sea-going, 



FIG. 18. Dredge "Cadiz." 



which are provided with self-propelling apparatus and stationary, 

 not equipped with propelling machinery, and must be towed from 

 place to place, and again we have the high- and low-tower types. 



Semi-sea-going ladder dredges have the hull so constructed as 

 to insure stability and steadiness to the machinery under the great 

 strain of the work rather than to give seaworthy qualities to the 

 steamer. The ratio between the length and width of the hull of 

 these dredges is smaller than in those of the sea-going type. To 

 allow the machine to work at various depths and consequently 

 with the ladder at different inclinations the hull is always open 

 and the walls of the pit are strengthened by a solid structure above 

 deck. The ladder well can be located at the bow of the steamer and 

 then the boilers and engines are aft, or vice versa. 



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