Typically the water was diverted from the river along a channel (as you can clearly see in the case of the third watermill) into a funnel. That increased the velocity of the water which turned the horizontal grinding stones. The force of the water striking a simple paddle wheel set horizontally in line with the flow turned a runner stone balanced on the rynd which is atop a shaft leading directly up from the wheel. These mills were not extremely efficient and that probably explains why there were so many in very close proximity.
The first watermill
The second watermill
The third watermill
The fifth watermill
The sixth watermill
and the Seventh watermill
