FLOATING AND RAFTING 



353 



The frame for rafter dams is frequently supported on round 

 or square timbers instead of crib work. 



Pile Dam. — The buttresses and wings of this type of dam are 

 formed by a double row of piles driven to bedrock, the space 



Photograph by E. R. McMillan. 

 Fig. 99. — The Sluiceway and Apron of a Rafter Dam on the Priest River. 

 Idaho. 



between them being filled with gravel and stone. The up- 

 stream face is banked up with brush and gravel to stop leakage. 

 This type is not in frequent use, although it was at one time 

 common in the Lake States. 



