Von Ebner's Fuze.—This form of fuze was devised by Colonel Von Ebner of the Austrian Engineers. A section and elevation of it is shown at [Fig. 28]. It consists of an outer cylinder, a, of gutta percha, and an inner one of copper, b, which latter encloses a core formed of ground glass and sulphur, c, which core is cast round the two conducting wires d, d in such a way that they are completely insulated from one another. In the first instance the wire is in one continuous length, the opening e being subsequently made, and carefully gauged, so as to ensure a uniform break, or interval in the conductor of each fuze. The priming composition, which consists of equal parts of sulphide of antimony and chlorate of potash, is placed in the hollow f, to which is added some powdered plumbago, for the purpose of increasing the conducting power of the composition. This mixture is put into the hollow, f, of the fuze under considerable pressure, the terminals being connected with a sensitive galvanometer, in circuit with a test battery, and the pressure applied so as to obtain, as far as possible, uniformity in the electrical resistance of each fuze.
The Austrians employed this form of high tension fuze in connection with a frictional machine for the electrical mines used in their defence of Venice, &c. during the war of 1866.
Abel's Fuze.—Mr. Abel devised a high tension fuze, which in 1858 was extensively experimented with; the Beardslee and Von Ebner fuze being based upon the principles applied for the first time in Abel's fuze.
ELECTRICAL FUZES.
Many modifications of it have been from time to time devised by Mr. Abel; a section and elevation of the more recent form of his fuze is shown at [Fig. 29]. It consists of b, b, a body of beech wood, hollowed for half its length, in which space the priming charge is placed; it is also perforated by three holes, one vertical for the reception of the capsule of sensitive mixture, the other two horizontal, in which the conducting wires are placed; a, a are two insulated copper wires, passing into the vertical hole, and resting on the sensitive mixture; in a cavity, d, of the body of the fuze is placed some mealed powder, which is fired by the ignition of the sensitive mixture on the passage of the electrical current.
The insulated wires used in connection with this fuze consist of two copper wires, about 2 inches long, and ·022 inch in diameter, enclosed in a covering of gutta percha ·13 inch in diameter, and separated about ·06 inch from each other.
At one end the wires are bared to 1·25 inch, at the other they are merely cut across by a very sharp pair of scissors. This end of the double covered wire is inserted into a paper cylinder c, c, which holds a small quantity of the priming mixture. This capped end of the wires is inserted into the wooden body of the fuze through the vertical hole i, and projects ·15 inch into the cavity d. The bare ends of the double covered wires are pressed into small grooves in the head of the cylinder e e, and each extremity is bent into one of the small channels d' d', which are at right angles to the vertical perforation. d' d' are two small copper tubes driven into these channels over the wire ends, to keep the wires in position, and to form the opening into which the conducting wires f are inserted and bent round, as at e'.
The priming mixture of Abel's original fuze, which was the one used by the Confederates, was composed of 10 parts of subphosphide of copper, 45 parts of subsulphide of copper, and 15 parts of chlorate of potash. These ingredients reduced to a very fine state of division, and intimately mixed, in a mortar, with the addition of a little alcohol, are dried at a low temperature and preserved in bottles until required for use. The sensitive mixture used by Mr. Abel more recently for his submarine electrical high tension fuzes, is composed of an intimate mixture of graphite and fulminate of mercury. By the process of ramming, the electrical resistance of the fuze is regulated.