16 BULLETIN 87, U. S. DEPARTMENT OP AGRICULTURE. 



torn of the flume. In consequence the water is forced over the sides, 

 and usually throws the material out of the flume, especially if the 

 curve is on an abrupt descent, or else the constantly increasing 

 weight of the jam breaks the legs of the trestle, if there be one at this 

 point, or perhaps causes the whole framework to collapse. It is then 

 often a matter of considerable loss of time and expense before the 

 flume is repaired and again ready for operation. The degree of 

 curvature should be kept as low as practicable, and should rarely 

 be permitted to exceed 20°. 



The length of material to be transported is an important factor in 

 deciding the degree of curve that can be used, since very long material 

 can not be successfully transported in a flume having a very abrupt 

 curve. The curve would have to be sufficiently open to allow the 

 chord of curve to be represented by the length of the longest material 

 desired to be handled, with a small allowance for clearance. No 

 curves should be used in construction that will cause the material 

 to "bind." The longer the material the less abrupt curvature is 

 permissible, and vice versa. The bracing of a flume on the outside 

 of the curve necessarily should be more rigid and stronger than on 

 the inside, since the greater pressure " thrust" or "throw" of the 

 water and material being shipped is toward the outside of the curve. 

 Very abrupt curves require increased bracing and the placing of the 

 arms and brackets at shorter intervals, in order to hold the flume 

 in its proper position. 



Shorter ' ' boxes ' ' and closer spacing of ' ' bents, " " arms, ' ' and ' - braces ' ' 

 on curves. — Where the topographic conditions in a locality are such 

 that it becomes absolutely necessary to have abrupt curves in a 

 flume, it is advisable to reduce the length of the boxes and correspond- 

 ingly shorten the distance that the "bents," "arms," and "braces" 

 are placed apart, for the twofold purpose of evening up or reducing 

 the sharpness of the angles in the joining of the boxes on the curve, 

 and also to give more stability and strength to the flume at the points 

 where there will be the greatest strain upon it. It will be apparent 

 that long boxes in a flume at a point where there was an abrupt 

 degree of curvature would necessitate sharper changes in direction 

 than would shorter boxes, thus producing something in the nature 

 of square corners. These corners, particularly if there were a rapid 

 descent in the flume line at such curve, would have an effect some- 

 thing in the nature of a dam or stoppage in the flume, and as a result 

 cause the water to slop over or run out over the sides. In addition, 

 all material coming down the flume, as a result of the quick change 

 in the direction of its course, would "strike" sharply against the 

 outside "comer," and the continual pounding of the material against 

 the side of the flume would be very likely to jar and eventually 

 loosen up the joints at this point, throw the flume out of alignment, 



