Confederate "current" Torpedo

This type of torpedo was attached to a length of rope, btween 250 and 350 feet long.  The opposing end of the rope was attached to a log.  With the rope stretched across the current, the torpedo and log assembly was floated down towards the enemy ship.  The hope was that the log would float down one side of the ship, and the torpedo would float down the opposite side.  The rope would catch on the ship's bow and wrap both ends around the ship's hull.  The rope was knotted, so as to catch on the ship's bow, to prevent the entire assembly from pulling off harmlessly.  Once the torpedo swung against the hull, held stationary by the rope, the current would catch the propeller on the torpedo, causing it to rotate down under the detent which released a hammer that struck a gun cap (some models used a percussion primer).  The gun cap would then set off the torpedo against the ship's hull.