FLUMES AND LOG SLUICES 
449 
the flume box becomes a wet slide and the logs run freely with 
very little water. The age of the flume and the care with which 
it is maintained largely determine the amount of leakage. Forest 
Service officials found that on the Allen flume in Montana which 
Photograph by H. H. Chapman. 
Fig. 165. — A Log Flume entering a Tunnel by means of which it crosses 
the Continental Divide. The flume runner is holding back some of the 
mining timbers so that they will not jam in the tunnel. The grade here 
does not exceed 0.5 per cent. Montana. 
carries from 5 to 12 second feet of water the leakage averaged 
0.3 second feet per mile. They estimate that the average leak- 
age in a flume in good condition carrying from 5 to 10 second 
feet of water will approximate 0.45 second feet per mile. 
Water for flume operation is admitted from ponds or branch 
flumes at the head and also at numerous points along the route 
