,CAUPOj 

 CHAPTER IX. 

 FLUMES AND THEIR STRUCTURE. 



¥p LUMES are boxes or troughs used to convey 

 •*■ I water where ditches are itnpra(5licable, or 

 w^m. needlessly expensive either to construdl or to 

 maintain. Where a ravine, valley, or any 

 considerable depression crosses the line of a ditch the 

 water may be turned into a flume, carried over the 

 depression, and then discharged into another ditch on 

 the further side. It may be advisable to carry the 

 water in a flume over loose sandy soil, where the loss 

 by percolation would be so excessive as to render a 

 sufficient delivery from an open ditch either difficult or 

 impossible. Special forms of sheet-iron or other sheet- 

 metal flumes are much used in mountainous secflions 

 because of their lightness, tightness and economy, and 

 the facility of eredling them in difficult places. As 

 usually construdled flumes are merely wooden boxes 

 open at the top and of such size and strength as is 

 necessary to carry, and support the water supplied. 

 Many in the west are of great size and strength, and 

 traverse great distances and at great hights. The 

 grades may, if necessary, be somewhat lighter and the 

 size smaller than those of the ditches supplying them, 

 because of the lesser fricflion and the greater facility of 

 flow. The volume of water to be carried will regulate 

 the size the same as in the ditches, and the grade will 

 in the same way regulate the carrying capacity by 



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