_Jointing Electrical Cables._--This is a very important point in connection with a system of defence or offence by electrical torpedoes. In many instances it will be found necessary to join either two lengths of cable, or an insulated wire and a cable, together, in both of which cases, great care must be used in making the joints, so that the insulation and the continuity of the circuit may be perfect. [Illustration: ELECTRIC CABLES, EXTEMPORE CABLE JOINTS. PLATE VIII] Many species of junctions have been from time to time devised, the most practical and generally employed of which are:-- 1.--India rubber tube joint. 2.--Mathieson's joint. 3.--Beardslee's joint. 4.--McEvoy's joint. 5.--Permanent junction. _India rubber Tube Joint._--This form of joint is a very useful one for extempore purposes, being easily and quickly made, and being very effective. At Fig. 34 is shown a sketch of such a junction. About 1·5 inches of the copper conductor of the two insulated cables are laid bare and connected together by means of Nicoll's metallic joint, as shown at Fig. 36, or by turning one of the conductors round the other, their ends being carefully pressed down by means of pliers, to prevent any chance of the india rubber tube being pierced; over the splice thus formed serve some twine, and over the whole put a coating of india rubber cement, grease, &c., then draw the vulcanised india rubber tube, which has been previously placed on one of the insulated cables, over the splice _a_, as shown at _b_, and secure it firmly by means of twine, _c_, _c_, and then to prevent any strain being brought on the joint, form a half-crown as shown in Fig. 35 at _A_. In forming the splice, it is very important that the metallic ends should be perfectly clean. The danger to this mode of jointing of the piercing of the tube by the ends of the conductors is entirely removed by employing the Nicoll metallic joint, which is formed as follows:-- _Nicoll Metallic Joint._--One of the conducting wires, as _a_, Fig. 36, is formed into a spiral twist by means of a very simple instrument, and the other wire _b_, which is left straight, is inserted into the spiral, the whole being placed on an anvil, and pressed closely and securely together by a single blow of a hammer.