Allowing for loss of head due to imparting velocity to water, and for contraction,
We hence have the following values of n, in v = n (r s)½, Q being constant:
| Rough ditch, with sharp curves. | 33 |
| Rectangular flume, with sharp curves. | 59 |
| Wrought-iron pipe, with easy curves, coated with asphalt, but with rivet-heads forming noteworthy obstructions (m = 65.5, and 2m = n) | 131 |
Vide pages 120-122, Transactions American Society of Civil Engineers for 1883.