Before revision: The front or toe extremities of these spring-boards are held by springs, or cocks and centered points, fixed to each of the treadle-boards E E; their back or heel extremities are left loose, to admit of elevation, when the springs are compressed (by the floor or any other means employed) by the descent of the treadles E E.
After revision: N is a crank allowing external operation.The front or toe extremities of these spring-boards are held by springs, or cocks and centered points, fixed to each of the treadle-boards E E; their back or heel extremities are left loose, to admit of elevation, when the springs are compressed (by the floor or any other means employed) by the descent of the treadles E E.