_High Tension Fuzes._--The high tension fuze was devised for use with electrical submarine mines, in the place of the platinum wire fuze, on account of the little knowledge possessed, in the early days of submarine warfare, in regard to the manipulation of Voltaic batteries. Platinum wire requires a temperature of some 500° F. to heat it to incandescence, and therefore necessitates the use of a powerful Voltaic battery, both in intensity and power, to effect the ignition of gunpowder by this means at considerable distances. The Grove and Bunsen pile were the only suitable form of Voltaic battery known at the period of the introduction of high tension fuzes, both of which possessed the defects of uncertainty and inconstancy, and also were by far too cumbersome and too difficult to keep in effective working order to be of any real practicable value. High tension fuzes may be ignited by means of either an electro-magneto machine, an electro-dynamo machine, a frictional machine, or by a Voltaic battery, generating an electric current of high intensity. Various kinds of this form of electrical fuze have been designed, the principal of which are as follows:-- 1.--Statham's fuze. 2.--Beardslee's fuze. 3.--Von Ebner's fuze. 4.--Abel's fuze. 5.--Extempore fuze. _Statham's Fuze._--A section and elevation of this electric fuze are shown at Fig. 26; _a_, _b_ is a gutta percha tube, with an opening cut in it, as shown in figure. The interior of this vulcanised gutta percha tube is coated with a thin layer of sulphide of copper, which coating is obtained by leaving a bare copper wire for some time in connection with the above-mentioned tube. The extremities of two insulated copper wires _c_, _c_, considerably smaller than the conducting wires, are uncovered, scraped, and then inserted into the tube _a_, _b_, with an interval of ·15 inch between them. The wires are then bent as shown in the figure, and the priming placed between the terminals. The whole is covered with a gutta percha bag, which is filled with fine grained gunpowder. The priming substance is composed of fulminate of mercury worked up with gum water. The objection to this fuze, which was used by the Allies in their destruction of the Russian fortifications at Sebastopol, is the want of sensitiveness of sulphide of copper, and the consequent necessity of a very powerful firing battery.