_In a chanel of running water, whose breadth is contracted by one or
more obstacles; the breadth of the chanel, the mean velocity of the
whole stream, and the breadth of the water-way between the obstacles
being given; To find the quantity of the fall occasioned by those
obstacles._
Let _b_ = breadth of the chanel in feet.
_v_ = mean velocity of the water in feet per sec.
_c_ = breadth of the water-way between the obstacles.