22 BULLETIN 87, TJ. S. DEPARTMENT OF AGRICULTURE. 
BRANCH FLUMES. 
Material is sometimes brought to the main flume from side gulches, 
ravines, or small watersheds by the use of what are generally known 
as "branch flumes." (See PL III, fig. 1.) Their use is advisable 
where there is a side valley with a sufficient volume of water availa- 
ble and containing enough material to make the construction of the 
branch flume warranted as being the most economical means of get- 
ting the material to the main flume. Branch or side-line flumes of 
this character are usually constructed practically the same as the 
main flume, except that it is usually advisable, if a mill has been 
constructed at the upper end of the main flume, to saw the lumber 
at the afread3 T constructed mill and flume it down to the most con- 
venient point of the main flume, where it is taken out and. from 
there hauled by team to the point at which it is to be used in con- 
structing the branch. Unless the branch were a long one, it would 
hardly justify the erection of a mill for the sole purpose of sawing 
out sufficient lumber to construct it. 
It is sometimes possible to take down a branch flume after the 
material in a gulch, small creek watershed, or ravine has been cleaned 
up, and move it to some other point and again set it up for use. 
Branch flumes are usually brought out and connected up with the 
main flume, as shown in Plate III, figure 1, so that the material being 
handled will come out into the latter on a gradual curve on the same 
level. Branch-flume lines also act as feeders and serve to mam tarn 
the volume of water necessary to operate the main flume. It will 
in some cases be f©und necessary to use the total volume of water 
available from two or more streams in order to have sufficient vol- 
ume to carry the material forward on the lower grades. In such cases 
it is sometimes possible to bring both the material and water together 
at the main flume by constructing the branch V flumes very strongly, 
and using them much as a wet slide is used to slip the material, by 
the aid of the small amount of water available, from the higher ele- 
vations down to where a sufficient amount of water has accumu- 
lated to float it to its destination. 
SWITCHES AND Y'S. 
Switches and Y's are sometimes necessary in the lower end of a 
flume when it is desired to direct material to different points for piling 
or to a planing mill, if it be lumber, or to storage places if it be railroad 
ties, cordwood, or mining stulls, when, as sometimes occurs, the ship- 
ping or transportation facilities are not adequate to take care of the 
amount of material being handled daily by the flume. (See PL V.) 
When this is the case and rough material is to be handled, it is advis- 
able to gradually raise the lower end of the flume on trestles, so as to 
have the desired space between the flume and the surface of the earth 
