FLUMES AND FLUMING. 
17 
and cause it to leak badly, or at least batter and wear it out more 
rapidly than would be the case if the curve were more gradual. 
More than this, there is always the increased danger of jams or blocks 
occurring in the flume at such points. It is for this reason that shorter 
boxes, which will more evenly graduate the curve, are desirable. 
There are no hard and fast rules that will correctly fit any and all 
conditions, but in general on curves of from 6 to 10 degrees, the boxes 
in a V-shaped flume should be " jointed" at least once in every 12 
feet with corresponding spacing of bents and reinforced bracing. On 
curves exceeding 10° and less than 15° the box should be jointed at 
least once in every 8 feet of length, and on curves of more than 
15° boxes should be jointed at least every 6 feet, with corresponding 
spacing of bents and reinforced bracing in every case. 
As said before, but repeated now for the sake of emphasis, when- 
ever it is possible without incurring too great or prohibitory expense, 
very abrupt curvature should be avoided in flume construction, and 
it will usually be found a wise policy to go to a considerable addi- 
tional expense in excavation work or blasting out of rocks and ledges 
in order to reduce curvature to a satisfactory degree. In every case 
where extreme curvature is unavoidable the foundation footings upon 
which the flume is supported should be carefully placed on very solid 
material, in order to withstand the continued impact and jar of the 
logs striking the sides of the flume ; and the entire flume construction 
should be strongly reinforced at such points, not only by shortening 
the length of the boxes and placing the bents, side arms, and braces 
closer together, but also, if trestling is necessary at such points, by 
strongly reinforcing the trestle bracing, both " lateral" and "sway. " 
Increase in height of sides of " V" on abrupt curves. — It is advisable 
on abrupt curves to increase or raise the height of the V on the 
outside of the curve, in order to cause the material being shipped to 
drop back into the flume when it tries to " climb, " as it always does 
in such places, and thus prevent it getting on top of the side of the 
flume and " riding" until it strikes some little projection or joint and 
forms a "block" or "jam." (See PI. II.) On very sharp curves 
it is usually advisable to raise both sides of the flume a little higher 
than is necessary on tangents and on equable grades, in order to 
retain the water in the flume, especially if there be a very abrupt 
descent at the point of curvature, as is sometimes unavoidably the 
case. The raising of the sides necessitates only the use of a longer 
arm and additional height of the lining of the flume at such points. 
FEEDERS. 
Feeders constructed at various points along a flume line are 
usually necessary in order to maintain the requisite amount of water 
and to furnish a sufficient volume to operate a flume successfully on 
33346°— 14 3 
