You know I've have been fortunate to have had the opportunity to work on the repairs and twice on the full replacement of the power source (turbine box) and the 12" oak axle, which passes through the box and exits on both sides, supported there on large split oak bearings
I might say right here that there is a tendency for the bearing on the off set crank side to wear at approx. twice the speed of the opposite bearing due to the wear and tear of the cutting action which comes from the cutting, jerking, and spinning of pitman and the saw blade
Now to get back to business --rotation direction of the turbine--
Well, I hope that at this point you have a grasp of how a horizontal barrel wheel works, but for those that do not it entails a hollow wooden box, circular on the inside, that is enclosed with iron collars that have cups that were moulded into them during the manufacturing process in a foundry
These collars run very close to the edges of the box to contain the pressure of the incoming water from the head race
as the water exited the box it struck the cups and rotated the shaft containing the offset crank in the opposite direction
That is an explanation of how the turbine works in a very brief description, but now the question of which direction of rotation is correct and why does it matter
Well it all boils down to this, the mill will work with the turbine rotating in either direction but very damaging wear will occur when the rotation is wrong, on the guide block above the turbine.