Head Gates
| The little building shown at the west end of the headrace in the 1909 view was a gatehouse that sheltered the head gates for the waterpower system at this site. The building is no longer standing, but the head gates remain. There are four gates in all. Built of thick layers of wood, the gates slide up and down so as to control the amount of water flowing into the headrace from the river upstream of the mill dam. The gates are raised and lowered by means of rack gears mounted to long vertical timbers (called stems) that extend upward from the gates. The middle two gates are smaller and have single stems; they are raised by means of hand-wheels connected to worm gears. The outer pair of gates are larger, double-stem gates operated by means of reduction gears. |  |
| The more the gates were opened, the greater the flow of water and, therefore, the more power that could be produced (within limits) by the various shops and mills along the headrace. If all the gates were closed at once, the headrace could be drained of water, something that might be done if maintenance was required. As part of the archaeological monitoring activities, the lower levels of the head-gate structure's masonry were exposed. Although the visible part was built of cut stone, the lower courses consist of a much more coarse rubble masonry. | |
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