58 War Science. " * [January, 



with any vessel passing over it. These machines are placed 

 in lines or groups in the channel to be defended, and are 

 capable of being exploded either by a sentinel on shore at a 

 particular moment or by concussion against any floating 

 mass or obstruction. Each torpedo contains, or is in com- 

 munication with, a large charge of gunpowder or gun-cotton, 

 and in the centre of this is placed the igniting fuse, an 

 instrument composed of two fine insulated wires, whose 

 poles — imbedded in a very sensitive explosive composition — 

 almost touch one another ; an electric current of but slight 

 intensity passing from one of these poles to the other is 

 sufficient to set lire to this composition and thus to explode 

 the charge, rendering necessary, therefore, the employment 

 only of batteries of but small dimensions. An insulated wire 

 leads from the battery on shore to one pole of the fu se, while the 

 other pole is connected with an insulated metal plate located 

 in the head of the machine. We should state that the top 

 of the torpedo has spread over it an iron cage or guard, some- 

 thing in the form of an open umbrella supported on a central 

 pivot, and the former, on being struck by any floating obstruc- 

 tion, swerves bodily round, and for the moment comes into 

 metallic contact with the insulated plate just mentioned, 

 completing in this way the electric circuit through the fuse ; 

 for the second pole of the latter has thus been placed 

 momentarily in contact with the battery on shore through 

 the medium of the earth, or, more strictly speaking, of the 

 water. An explosive machine of this nature is termed a self- 

 acting torpedo, and will probably be that most suitable for 

 warfare, but a modification of it, also fitted with this electric 

 fuse, will be likewise employed for ignition from the shore. 



The great advantage of these torpedoes lies in the employ- 

 ment of the Abel fuse just described, which, besides pos- 

 sessing the qualifications of an ordinary electric fuse, allows 

 of a current being sent through them at any time to test 

 their efficiency without the slightest risk of explosion, 

 provided, always, the battery employed for the purpose is a 

 comparatively weak one ; signals may also be passed through 

 the fuse in like manner, should the charges happen to be 

 planted midway between two stations, and a torpedo 

 system may thus be used in the absence of other telegraphic 

 communication. 



Contrived upon this plan we see at once that a system of 

 torpedo defence becomes one of the most effective and con- 

 trollable means of harbour protection that can possibly exist; 

 until the actual approach of an enemy the batteries may be 

 kept entirely disconnected from the machines, and the latter 



