200 



A TREATISE ON DREDGES AND DREDGING 



is placed at the center of the apparatus and is supported by two 

 independent floats, each of them affording a firm support for one 

 of the standards of the tower. Besides, the floats are connected 

 together by a bridge provided with a gantry for raising the ladder. 

 The scows enter the space between the floats, passing under the 

 bridge. The unloading is very simple. The ladder that was raised 

 to allow the scow to enter is now lowered into the hold, the machine 

 is put in motion, and the buckets filled with materials travel along 

 the ladder and dump their contents over the upper tumbler, dis- 



FIG. 69. Floating Elevator for Unloading Barges. 



charging into a long chute which delivers the materials to the land to 

 be filled. The long chute can be supported in the manner indicated 

 in the figure, or when the elevator is located too far from shore 

 the chute can be supported by means of another float and in the 

 manner already described on page 186. The ladder may con- 

 tain only one series of buckets, like any ladder dredge, but owini; 

 to the fact that the buckets used are of small capacity, to hasten 

 the unloading operation and at the same time to prevent increasing 

 the size of the buckets, thus producing too much strain on the bot- 

 tom of the scows, two series of buckets are usually mounted on 



