190 A TREATISE ON DREDGES AND DREDGING 



from one pontoon for 50 ft. of its length by the trough of a wave, 

 its weight could be rested upon the adjoining pontoon with safety. 

 No anchorage is used at any intermediate point of the pipe. 

 It is attached at one end to the dredge and at the other by a short 

 cable to scow, the entire 2000 ft. being free to drift as it pleases. 

 The scow is fitted with a steam winch, by which its own anchorage 

 is controlled. It has two anchors with wire cables 1-J in. diameter 

 and 2000 ft. long. These can be hauled in and paid out as required 

 and this movement serves both to distribute the material, to avoid 

 piling up above the surface of the water, and also to regulate the 

 tension of the pipe when the dredge is making a very wide cut. 

 In places, when the cut is 750 ft. wide the pipe tightens up to almost 

 a straight line when the dredge is at the far side. The scow anchor- 

 age permits considerable freedom of movement, and, when neces- 

 sary, the operator on the scow pays out on his anchorage to relieve 

 and permit the dredge to make the cut. 



FIG. 61. Open-hold Barge. 



Scows. The scows used for the transportation of the dredged 

 materials are of different types, which for sake of classification can 

 be grouped in open-hold scows, deck scows or floats, and dumping 

 scows. Each group can be subdivided again. 



Open-hold Barges. The ordinary barges or lighters used for the 

 transportation of various materials along canals and rivers can be 

 also employed for carrying away the dredged debris. As a general 

 rule these vessels are not the most convenient and economical, 

 yet there are cases in which even these barges can be employed with 

 advantage. In the open-hold barges the material is deposited 

 directly on the bottom of the boat, the floor being formed by plunks 

 placed longitudinally and resting on the keelsons Fig. 61. The 

 empty space included between the said platform and the sides of the 

 boat determines the capacity of the vessel, which capacity varies con- 

 siderably. This type of barge is very seldom used for the transporta- 

 tion of the dredged materials, owing to the difficulty of removing the 

 debris from the bottom of the scow. It is only used in the improve- 



