Right beside the Babcock Mill itself sits an, often unforgotten, building. It is directly linked to the mill via a metal rod which comes out the side and runs underground into the mill. There is an water trench on the backside that runs into the bottom section of this building.
Inside you can find an assembly system complete with gears, chains, and other machining parts. There is also a bench in there and an assortment of old wooden tools and other various wooden items. On the far side, there are stairs that lead down and some sort of belt that followed down with it.
*WARNING* - There is a big hole in the floor just inside the bench area. Even in broad daylight it is very dark. Please be careful and watch your step.
At the bottom of this hole was some sort of some giant wheel with gears and various other moving parts. Judging by this and the water trench, I can only assume that it was some sort of power source to the main milling building.