Detail of a Mill's Screw and Drive Mechanism
A screw of six threads turning a fork three times; the recto's bridge shows through above
At the lower right a mill mechanism is drawn: a dome-topped table frame carrying a large wheel geared to a pair of upright cylinders. The accompanying note specifies that the mill's screw should have six threads and will turn the 'fork' three times, and it is keyed to a small striped drawing of the screw itself. The faint structure filling the upper part of the sheet is show-through of the covered bridge drawn on the recto.
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Screw of the mill: six threads, three turns of the fork
The screw of this mill is to be set as drawn, given six threads, and made to turn the fork three times. A small striped cylinder beside the note shows the threaded screw.
Dome-topped mill frame with wheel and cylinders
A table-like timber frame supports a dome and carries a large spoked wheel geared to two upright cylinders. The arrangement illustrates the drive into which the screw described in the note fits.