STATIONARY AND HIGH-TOWER LADDER DREDGES 91 



Many engineers object to this type of dredge, while there are 

 others who absolutely condemn it as obsolete. But when it is 

 considered that in the ladder dredges, the coal consumption repre- 

 sents only 10 or 15 per cent of the running expenses, it is easily 

 realized that the cost per unit of volume of the dredged materials 

 will not be greatly affected by even doubling the cost of fuel. On 

 the other hand the great advantage of these machines consists in 

 the fact that they convey the dredged materials to the dumping 

 place without additional cost of transportation. Consequently 

 the small increase in the cost of dredging is more than compensated 

 by the free conveyance of the debris to the dumping places. Another 

 advantage of the high-tower ladder dredge consists in the fact that 

 working day and night it will perform the work of two machines, 



FIG. 24. High Tower Ladder Dredge "City of Paris." 



thus greatly reducing the cost of the plant and the general expenses. 

 Even to-day these high-tower ladder dredges in some classes of work 

 will give the same satisfactory results as they did along the Suez 

 Canal in the early days of their existence. Over one-third of the 

 Suez Canal was excavated by means of these high-tower ladder 

 dredges, and they were found very efficient in dredging the lower 

 sections of the Panama Canal during the French Administration. 



The following description of the dredge "City of Paris" taken 

 from the Scientific American, serves to illustrate a high-tower ladder 

 dredge built in the United States, and used by the American Contract- 

 ing & Dredging Co. of New York for the Panama and Nicaragua 

 Canals. Shown in Fig. 24. 



The typical American dredge, represented by the " City of Paris," 

 is provided with composite hull 115 ft. long and 56 ft. wide. In 



