FLUMES AND FLUMLTSTG. 19 



minimum. This will permit of the u stringers" for the flume resting 

 on solid foundation in the bottom of the tunnel, which, once solidly 

 placed, usually requires little or no repair. 



There is no danger of flumes constructed through tunnels being 

 filled as a result of snowstorms nor affected by contraction or warping 

 as a result of the sun's rays. The principal danger resulting from 

 construction through tunnels is that of material falling into the 

 flume from the top of the tunnel, unless it is protected, when the 

 tunnel is through loose earth, by framework and lagging over the 

 top of the flume. This danger, of course, does not exist where a 

 tunnel is driven through solid rock, as the rock itself furnishes a 

 stable roofing. And if the earth through which the tunnel is driven 

 is solid, it is not always necessary to go to the expense of setting up 

 frames and placing "lagging" over the top of the flume, since what 

 small amount of loose earth does drop into the flume as a rule will 

 quickly be dissolved and washed away by the running water. It is 

 usually possible, by varying the flume-fine location, to get around 

 obstacles without going to the expense of driving a tunnel through 

 rocks and ridges, but there will be found cases in which it is im- 

 possible to secure a satisfactory location and at the same time 

 maintain a desirable grade and avoid very abrupt curves without 

 resorting to tunneling. 



SMALL HOLDING RESERVOIRS AT DIFFERENT POINTS OF FLUME. 



It is sometimes advisable to have small holding reservoirs or 

 " catch basins" constructed at different points along a flume line, 

 where it can be done without involving prohibitive expense, in order 

 to provide an additional storage place for logs, crossties, or rough 

 lumber. The upper end of a flume may have to be used to its fullest 

 capacity for a short time in the spring, when the melting snow and 

 early spring rains will furnish a sufficient volume of water to transport 

 material down to the upper end and past more abrupt portions of the 

 flume, and sometimes when this rapid shipment is going on, loading 

 or storage facilities at the lower end of the flume may become so 

 congested that it is impossible to take care of all the material, even 

 temporarily, at that end. 



Under such conditions it is sometimes possible to construct at differ- 

 ent points along the line of the flume small storage reservoirs, which can 

 be cheaply formed by damming up some small stream or using some 

 small natural pond favorably located along the line, thus diverting 

 the class of material not desired to be handled clear through at once 

 into such reservoir, and taking it out and shipping it later with the aid 

 of the increased volume of water available at this lower point of the 

 flume. The prospective operator must always be his own judge of 

 whether this is necessary and desirable, and should properly take into 



