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HINTS ON SELECTING DREDGES FOR VARIOUS WORK 55 



scows are used and the material pumped directly from the scows. 

 As a rule the second handling generally costs more than the first. 



When dredges work in sheltered harbors or in rivers and canals 

 it is not necessary to have them self-propelling, but when they are 

 used in exposed places or go to sea it is safer to have a self-propelling 

 machine. Many large dredges are self-propelling even when designed 

 for river work, as it is more economical to move them great distances 

 without the aid of tugs and it is easier to maneuver them while 

 at work. 



Non-propelling dredges are handled when at work by means 

 of spuds and by anchor lines. For small dredges the lines are 

 handled by small rowboats and capstans on the deck of the dredge, 

 but for large machines anchor scows are sometimes used. These 

 are small scows with a windlass and capstan on it to handle the 

 heavy anchors, and the lines are run from the scows to the dredge. 



When anchor lines are used the maneuvering of the dredge while 

 at work must always be planned so as not to interfere with the passing 

 of vessels. The work should be done so that delays happen neither 

 to the dredge nor to the vessels. 



