In crossing ravines in this State, flumes or wrought iron pipes are used. Many miners object to flumes on account of their continual cost and danger of destruction by fire. Where used and practicable, they are set on heavier grades than ditches, 30 to 35 ft. per mile, and, consequently, are proportionately of smaller area than the ditches. In their construction a straight line is the most desirable. Curves, where required, should be carefully set, so that the flume may discharge its maximum quantity. Many ditches in California have miles of fluming. The annexed sketch, drawn by A. J. Bowie, Jr., will show the ordinary style of construction.
SKETCH OF FLUME.
The planking ordinarily used is of heart sugar pine, one and a half to two inches thick, and 12 to 18 inches wide. Where the boards join, pine battens three inches wide by one and a half thick cover the seam. Sills, posts, and caps support and strengthen the flume every four feet. The posts are mortised into the caps and sills. The sills extend about 20 inches beyond the posts, and to them side braces are nailed to strengthen the structure. This extension of the sill timbers affords a place for the accumulation of snow and ice, and in the mountains such accumulations frequently break them off, and occasionally destroy a flume.
To avoid damage from slides, snow, and wind storms, the flumes are set in as close as possible to the bank, and rest, wholly or partially, on a solid bed, as the general topography and costs will admit. Stringers running the entire length of the flume are placed beneath the sills just outside of the posts. They are not absolutely necessary, but in point of economy are most valuable, as they preserve the timbers. As occasion may demand, the flume is trestled, the main supports being placed every eight feet. The scantling and struts used are in accordance with the requirements of the work.--Min. and Sci. Press.