Here, you can see the hole in the roof. I have no idea how long the hole has been there, and the general condition of the power house is remarkably good (it does not feel shaky, for example), considering the hole in the roof. However, with such a substantial leak, the structure will rot from the inside, eventually.
This picture also shows clearly the T-shape of the power house. The drive pully and the governor are in the "top" of the T, the drive belt from the drive pully to the generator formed the "I" of the T, and the generator was at the foot (just inside the door, although not visible in this picture).


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