FLUMES AND LOG SLUICES 445 
Curves at the base of steep p;ra(les should be avoided, l)ecause 
jams will form which will not only damage the flume but will 
also cause the lumber to leave it. The most desirable grades 
for a straight flume are 3 per cent or more. Grades up to 75 
per cent may be used on short stretches, provided all sharp changes 
in elevation have properly proportioned vertical curves. 
CONSTRUCTION 
The general methods of constructing a V-fiume may be illus- 
trated by one built in Washington for the daily transport of 40,000 
board feet of lumber and crossties which ranged in length from 8 
to 32 feet. 
The flume had a maximum height of 128 feet, maximum 
curves of 8 degrees, and a 3 per cent grade on the upper part 
and 0.66 per cent on the lower end. Lumber floated at an average 
rate of 3 miles per hour. 
Bents were placed 15.75 feet apart for heights of 65 feet and 
under, and 23.5 feet apart for heights in excess of this. The 
batter posts on all trestles under 75 feet were spaced 4 feet apart 
at the cap, and for heights greater than this 5 feet. The batter 
in all cases was 1 in 4. In the bent construction only three 
sizes of lumber were used, namely, 1- by 6-inch, 2- by 6-inch, 
and 2- by 4-inch, the latter being used for the fore-and-aft brac- 
ing. As a rule only 16- and 24-foot lengths were used, because 
this simplified the work, reduced the time lost in handling, and 
very little lumber was wasted. A ''select common" grade of 
lumber was used. The first 24-foot section of each bent was 
framed on the ground, the foot of each batter post being laid 
on or near the mud-sill on which it was to rest. Bracing was 
made from 1- by 6-inch and 2- by 6-inch material. When ready, 
the bent was hoisted in place, and set on the mud-sills by the aid 
of a block and tackle attached near the top of the nearest bent. 
When in position it was plumbed up and spiked to the mud-sill. 
A scantling 2 by 6 inches by 16 feet was then placed against the 
outside of each post and securely nailed to it with 20-penny 
spikes. Fore-and-aft braces (Fig. 160) were then nailed on until 
the top of the 16-foot post was reached when another 2- by 6- 
inch by 24-foot scantling was set on top of the first post with a 
lap of 16 feet on the inner one. More fore-and-aft braces were 
then placed. The addition of 2- by 6-inch by 24-foot scantlings 
