6 BULLETIN 87, U. S. DEPARTMENT OF AGRICULTURE. 



(4) In cases where it is necessary to have an unusually abrupt 

 descent in some portions of the grade, the V-shaped flume is best 

 adapted to serve as a "slide" or "slip," or "chute," since it is less 

 likel} r to become jammed, while the material being handled is held 

 by its own weight in proper position in the center of the V. In a 

 great many localities this particular feature of control of the log 

 or stick of timber when it is "coasting" will be found very neces- 

 sary in handling material from the higher mountain slopes, espe- 

 cially in places where it is impossible to maintain a steady and 

 equable grade from the top to the bottom of the mountain without 

 too great expense, and where it may be necessary to have a form 

 oi construction that will carry logs or timber safely for a long dis- 

 tance when the grade is so abrupt that it is impossible to maintain a 

 sufficient volume of water in the flume to prevent the material from 

 rubbing or sliding along on the sides and bottom. In such localities 

 and under such conditions the V-shaped flume, when strongly con- 

 structed so as to combine both the objects of flume and chute, has 

 been and will be found altogether the most desirable. 



DEGREE OP ANGLE FOR "V "-SHAPED FLUME BOXES. 



In the construction of the sections or "boxes" in V-shaped flumes 

 a number of different degrees of angles have been used in the past. 

 In some instances the constructors have used an angle as low as 70 

 degrees, while others have constructed flumes with an angle of 110 

 degrees. The results of experience and the consensus of opinion, 

 however, are that the 90-degree or straight right angle is the most 

 satisfactory form of V-box construction for all purposes, and this is 

 the degree of angle that is referred to when speaking of V-shaped 

 flumes in this bulletin unless otherwise specifically stated. 



METHODS OP CONSTRUCTING THE "v "-SHAPED PLUME. 



There are many different methods and styles of construction used 

 in building V-shaped flumes, varying according to the kind of material 

 to be handled. In some cases the brackets or frames that support 

 the sides of the V are made from round pole wood simply flattened 

 on one side so as to give an even surfaced support to the boards 

 forming the "lining" or inside of the V, while the sills, stringers, 

 braces, and trestling may be constructed from small round timber 

 or poles, leaving only the lining or inside of the box to be constructed 

 from sawed lumber. The form of construction of the different sec- 

 tions of the flume, or, as they are called, "boxes," also varies in length 

 from short ones of 6 feet up to those of 20 feet. In the con- 

 struction of the lining or inside of the boxes, lumber of variable 

 thickness and width is used. The boxes are sometimes made of only 

 one thickness of boards simply joined together, but more commonly 



