Taffrail Log Recorder, Patent Model

This high-quality working example of a Taffrail Log was submitted to the U.S. Patent Office when John Edward Massey, its British inventor, applied for a patent in 1877. This two-part mechanical log measures a vessel's speed though the water. The four-bladed rotator is towed astern and registers the distance traveled and speed on an integral dial. Closer to the ship, or even mounted to the ship's rail, a second mechanism measures rotations of the towing rope to record the same information. The rotator must be hauled in to be read, but the second log can be monitored while the first is still in operation.

Since the sixteenth century, sailors had determined vessel speed using a log. This device was basically a ...