This "Nantucket" style harpoon log was made by John Hand & Sons, instrument makers in Philadelphia- it bears their name and logo a hand with compass on the face and on one of the fins. This mechanical log tells the distance the ship sails through the water by recording the number of times the finned section of the mechanism turns. The indicator shows nautical miles sailed, in hundreds, tens, and ones. The log was towed astern of the ship and hauled in for readings.