CLASSIFICATION AND CAPACITIES OF DREDGES 63 



paddle-wheel located at the stern, as used on some dredges employed 

 on the Mississippi River, and in the dredge "Edward VII" shown in 

 Fig. 37. The single stern wheel may also be provided with spikes, 

 which engage the soil at the bottom of the river and canal. Special 

 dredges employed by the French Government on the River Rh6ne 

 have been so constructed. 



Dredges may also be grouped according to the manner of disposing 

 of the excavated materials. Thus the dredges may discharge the 

 materials into hoppers of large capacity contained in their hulls, 

 thus carrying and dumping their loads in deep waters. These are 

 the sea-going dredges of the hopper type. Sometimes, though, the 

 hull may be only large enough to carry the required machines and 

 coal bunker or there may be room to provide accommodations for the 

 officers and crew. Then the dredged material is disposed of in 

 different ways. It can be discharged into scows to be dumped 

 into deep water, or deposited wherever desired, as is commonly 

 done with the ladder, dipper and grapple dredges. The material 

 can also be dumped directly alongside the dredged 'channel, thus 

 using it to form a levee. This method is used with the dipper and 

 grapple dredges employed in cutting canals or dredging narrow 

 rivers, and sometimes even with ladder dredges, but chiefly with those 

 of the high-tower type. All the hydraulic dredges and some of the 

 ladder dredges working through very loose soils, when they are not 

 of the hopper type, discharge the excavated material through long 

 line of pipes using it for filling lowlands, as is commonly done 

 in reclaiming low, swampy ground. 



The simplest manner of disposing of dredged material is the one 

 used in connection with the stirring process. This consists in stirring 

 up the material at the bottom of the water, thus bringing it to the 

 surface by agitation and by allowing the velocity of the water to 

 carry it away. Such a method, however, although very convenient 

 and economical, is very seldom used, as it requires conditions that 

 cannot be controlled by the engineer. This method, though, has 

 been used on the Mississippi River and in the harbor of Swansea in 

 England. 



There are many dredges built of special design or meant for 

 some particular piece of work, yet even when used on land they can 

 be considered under the classification given. The main consideration 

 should always be the adaptability of dredge. 



In the United States dredges of many designs are used, and until 



