Nikola Tesla's patents for aircraft, ships, railways, autos, and more

Ship's Log

It was also necessary to improve the way in which ships calculated their speed either in knots or miles per hour. Common ship's logs of the time were trailed behind the ship and were difficult to read. Tesla's Ship's Log, however, was mounted on the bow of the ship below the keel with a speed indicator mounted on the ship where it was easy to see.

Image courtesy of Tesla Universe