As we pulled along he gave us an explanation of the fish torpedo--a wonderful instrument of destruction which has been invented of late years.  It is a cylinder, which carries the explosive material at one end and the machinery for working the screw which impels it at the other.  It can be discharged through a tube with such accuracy that it can strike an object several hundred yards off.  On getting on board the old frigate, we found a large party of officers assembled.  We were to witness the explosion of two other sorts of torpedoes.  One was used by a steam launch, the fore part of which was entirely covered over by an iron shield.  The torpedo was fixed to the end of a long pole, carried at the side of the launch.  At some distance from the ship a huge cask was moored, towards which the launch rapidly made her way.  The pole, with the torpedo at the end, was then thrust forward; the concussion ignited it the instant it struck the cask and blew it to fragments.