206 A TREATISE OX DREDGES AND DREDGING 



method of keeping this sediment out of the river is to narrow the 

 stream and protect the banks by revetments in the flat parts of the 

 river, as these prevent the stream from further eroding the hanks, 

 and the narrowed channel means a swifter current that will keep 

 the sediment in suspension. Then at the mouth of the river jet i jVs 

 can be constructed that causes the current to sweep the channel 

 clear and carry the sediment into the bay or ocean. 



The source of the St. Lawrence River is in the Great Lakes, 

 which act as huge storage reservoirs and settling basins. Except 

 for floods caused by the melting and breaking up of the winter ice 

 the fluctuations of the river are always gradual. Thus the material 

 usually carried by river water is deposited in the settling basins, 

 this being the case even with the few streams that flow into the 

 St. Lawrence, as the so-called lakes and bays, as Lake St. Peter, 

 act as settling basins for such streams. Generally, the bottom of 

 the river is hard, and although in many places this makes difficult 

 dredging, yet once dredged, the work is permanent. The currents 

 of the river are regular, and although there is little danger to vesseb 

 that navigate the river, yet the water at times becomes rough from 

 sudden squalls, compelling the dredges to suspend work and seek 

 sheltered places. The season of dredging is about 1\ months. 



As the material dredged is dumped into the river at places 

 where it will not interfere with navigation, it is seen that this work 

 does not theoretically nor practically lower the level of the water. 



The following plant was used on the river during the season 

 of 1907: 



6 elevator dredges. 



1 hydraulic dredge with 23 double pontoons, floating a 2300-ft. 

 double line of pipe, and 2 winch scows. 



1 twin-screw self -containing hydraulic dredge. 



1 twin-screw sea-going pump dredge. 



1 ice-breaking and sweeping tug and 1 testing or sou ml in L\ 

 scow used with it. 



I inspection tug. 



I 1 tugs for serving dredges. 

 4 coal barges. 



1 coal scow. 



2 stone lifters. 



6 lodging scows. 

 14 hopper scows. 



