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other reasons it is improbable that any more lumber-carrying flumes 
will be constructed in California, except in instances where a railroad 
or incline is clearly impracticable. 
There are several flumes now in successful operation in California, 
though the number in use is gradually decreasing. The longest ones 
are located in the southern Sierras, where longer and more expensive 
railroads are required to reach merchantable timber than in the 
northern part of the State. The lengths of the three flumes in the 
southern Sierras are respectively 42, 56, and 60 miles. On the 
other hand, one flume located in northern California is only 4J 
miles in length. 
These flumes consist of a V-shaped box with sides 32 inches wide 
in the mountains and 48 inches wide where the grade is low and the 
water sluggish. The angle formed by the sides of the flume is a right 
angle, and the width across the top is 46 inches where the sides 
are 32 inches wide. The flume *box is supported at distances of 
either 8 or 16 feet by bents composed of 4 by 6 inch or 6 by 6 inch 
fir timbers. In the original construction bents were placed at 
16-foot intervals, but it has been found advisable to place supports 
every 8 feet for low trestles. Higher trestles are still constructed 
with 16-foot bents, but heavier timber and sway and stringer braces 
are used. Two 4 by 6 inch stringers are supported by the bents. 
Upon the stringers at intervals of 4 feet are placed the braces which 
hold the flume box in an upright position. 
The cost of constructing flumes varies with the difficulty of pre- 
paring the ground for foundations and the average height of the 
bents; with lumber at $12 per 1,000 it ranges from $20 to $25 per 1,000 
board feet, the higher cost being where the average height of the 
flume is least. The lowest recorded cost is for two flumes in northern 
California, approximately $4,000 per mile. In the southern Sierras 
the natural conditions affecting construction are more difficult, 
and the average cost of construction is about $5,000 per mile. The 
most expensive flume in that locality is reported to have cost $6,000 
per mile. The average amount of material is from 225,000 to 275,000 
feet per mile. Farther north the average is not over 175,000 feet. 
The maximum grade allowable is about 25 per cent for short 
pitches. Normally the grade is kept down to between 5 and 10 
per cent, with 12 per cent as a maximum. In the San Joaquin 
Valley the grade is very low. One flume in which the lumber is 
shipped in bundles has approximately 13 miles on the lower end 
with a grade of only 0.13 per cent. Another in which the lumber 
is shipped loose has a similar length of slack water with a grade of 
0.26 per cent. The maximum curve used is about 20 degrees. The 
volume of water required to operate a flume varies from 25 to 35 
second-feet. 
