§ 97. _Coefficient of Friction for Open Channels._--Various
expressions have been proposed for the coefficient of friction for
channels as for pipes. Weisbach, giving attention chiefly to the
variation of the coefficient of friction with the velocity, proposed
an expression of the form
[zeta] = [alpha](1 + [beta]/v), (5)
and from 255 experiments obtained for the constants the values
[alpha] = 0.007409; [beta] = 0.1920.