Thanks Jerseyman once again for enlightening us.
Your thoughts on the power canal are probably spot on in this case.
In pipe design, the velocity (V) in the pipe is a function of Q (flow in Cubic feet per second) divided by the cross sectional area A (of the pipe.
V= Q/A
To increase velocity, given the same flow, you can reduce cross the sectional area of the conduit. (Pipe or canal in this case)
At Bispham's Mill, the flow we observed in the stream in its natural condition was very high.
By diverting a portion of that flow into a narrow conduit you would greatly increase its velocity and thus its power to do work.
If one has ever used a small diameter hose nozzle on a household garden hose you have seen this principle at work. You can blow paint off with some of them. The available flow from the house is a constant, the velocity increases because the area at the end of the hose has decreased.
Couple that with the hydraulic head between Bispham's and New Lisbon(difference in elevation) and you really got some power.
After I heard you use the term power canal I Googled it and found this great visual of a large scale power canal.
http://upload.wikimedia.org/wikiped..._Canal_(Turners_Falls,_Massachusetts)_map.jpg
Note the amount of constriction after it comes in from the river.
And just think, our forefathers had all this figured out without using a formula or a calculator.
Scott