FLUMES AND THEIR STRUCTURE. 105 



provides a means of fastening the flume to the bracket. 

 Figure 35 shows a larger flume half circular in section, 

 supported by a bracket at each side resting on horizontal 

 timber. In both these cases the board beneath the flume 

 may be omitted, but it aids in erection, and adds stability 

 to the structure. The smaller sizes do not have riveted 

 connections between joints, and therefore, especially in 

 the use of the single post support, may be easily moved 

 from one locality to another. 



The general shape of the flumes in section is para- 

 bolic. Where depth is restricted and the volume of 

 water to be carried is large, the type shown by Figure 3G 



FIG. 36. CROSS SECTION OF LARGE IRON FLUME. 



i.s a ilopted, the sides being parabolic and the bottom cir- 

 cular. In this case the bottom of the flume is sup- 

 ported throughout its entire length by plank or timber 

 on edge let down into the sill of the trestle to conform 

 to the shape of the flume. 



In case it is desired iron may be substituted for the 

 timber supports. Figures 37'and 38 show how admirably 

 this form of flume may be adapted to a rough country, by 

 resting one end of the sills on a precipitous rock wall 

 and supporting the other on timbers, or by means of 

 rods and eyebolts driven into an overhanging cliff. 



