| 摘要 |
A chronometer having a tide grid comprising a contour line indicating at least one complete tide cycle and a superposed reading grid comprising at least one read-off reference mark. One of the grids is driven in rotation at a constant angular speed about an axis. The grids are concentric about that axis and the read-off reference mark is radially disposed relative to that axis The contour line indicates tides on polar coordinates such that the distance of a point on the contour line from that axis indicates the height of the tide. The radial read-off reference mark intersects the contour line at a point which indicates the height of the tide for the time shown by the chronometer for a specific geographical location.
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