FLUMES AND FLUMING. 19 
minimum. This will permit of the " 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 w T arping 
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 wall 
quickly be dissolved and washed away by the running water. It is 
usually possible, by varying the flume-line 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 
lc 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 
