During September, 1899, the Marconi method of signalling to long distances was demonstrated before the British Association at Dover. The chief feature of the installation was the elevated wire supported by a mast, and terminating at the top in a small conductor, which is usually made of wire netting, and is suspended from an insulating rod. The lower end of this elevated wire passed into the building through an aperture, and was connected to one terminal of the usual Ruhmkorff coil, the other terminal of which was earthed. The signalling key was of the simplest description, being nothing more than a well-insulated Morse key worked by hand and causing a make-and-break in the primary circuit of the coil. The ordinary trembling break of the induction coil was at work in the usual way, so that while the signalling key was depressed continuously there was a torrent of sparks between the knobs of the secondary. This method of signalling was identical with that employed by everyone since the time of Hertz, except that, instead of connecting the secondary terminals to two insulated plates, one was now connected to earth and the other to a small insulated conductor at considerable elevation. [Illustration: FIG. 48 (Fig. 11 of Prof. Slaby’s book on “Spark Telegraphy”).] [Illustration: FIG. 49 (p. 762, _The Electrician_, Vol. XLIII.).--Marconi Signalling Mast at Dover Town Hall.] [Illustration: FIG. 50 (Fig. 1, p. 7, _The Electrician_, Vol. XLIII.).--Mast at South Foreland; from which Signals went to a similar Mast at Wimereux, near Boulogne.]