--------+------+-------+-------+-------+-------+-------+------- Velocity| Diameters in Feet (_d = 4r_). _v_, | Feet per+------+-------+-------+-------+-------+------- Second.| 3.5 | 4 | 5 | 6 | 7 | 8 --------+------+-------+-------+-------+-------+------- 1 |120.2 | 123.0 | 127.8 | 131.8 | 134.8 | 137.5 2 |127.0 | 129.9 | 134.3 | 138.0 | 141.0 | 143.3 3 |131.4 | 134.2 | 138.6 | 142.3 | 145.4 | 147.6 4 |134.6 | 137.4 | 141.9 | 145.5 | 148.6 | 151.0 5 |137.1 | 140.0 | 144.7 | 148.1 | 151.2 | 153.6 6 |139.4 | 142.3 | 146.9 | 150.5 | 153.5 | 7 |141.5 | 144.5 | 149.0 | 152.7 | | 8 |143.3 | 146.3 | 151.0 | 154.9 | | 9 |145.0 | 148.1 | 152.8 | 156.7 | | 10 |146.4 | 149.7 | 154.6 | | | 11 |147.7 | 151.0 | | | | 12 |148.8 | 152.3 | | | | 13 |149.8 | 153.2 | | | | 14 |150.5 | 154.0 | | | | 15 |151.1 | 154.6 | | | | 20(?)| | | | | | --------+------+-------+-------+-------+-------+------- =194. Timber-stave Pipes.=—In the western part of the country long conduits or pipe-lines are frequently constructed of timber called redwood. Staves of suitable thickness, sometimes 1¾ inches, are accurately shaped and finished with smooth surfaces so as to form large pipes of any desired diameter. These staves are held rigidly in place with steel bands drawn tight with nuts on screw ends, so as to close tightly the joints between them. Such wooden conduits are rapidly and cheaply built and are very durable. They have the further advantage of requiring no interior coating, as the timber surface remains indefinitely unaffected by the water flowing over it. The latter part of Table XV shows coefficients for Chezy’s formula which may be used for such a class of timber conduits. As the interior surfaces of such closed conduits are always very smooth, the coefficients are seen to be relatively large, and such pipes are, therefore, well adapted to maintain unimpaired discharging capacity for great lengths of time. CHAPTER XVIII.