TELEGRAPHY, WIRED-- 



717 



rapidly broken and reformed, with a shrieking noise. 

 This device will work only on an inductive circuit, 

 and its action has not yet been fully explained. 

 Its value for wireless telegraphy and for skiagraphy 

 lies in the facts that it can be used with the ordi- 

 nary street main, and that it gives out absolutely 

 continuous trains of waves. It is likely to play an 

 important part in the development of space sig- 

 naling. (See " Engineering," London, March 17, 

 1899.) 



Among Signor Marconi's first achievements with 

 his apparatus was the sending of messages across 

 Bristol Channel, more than 9 miles. Later, in Italy, 

 he telegraphed from the fortress of San Bartolomeo 

 to the warship " San Martino," 12 miles out at sea. In 

 this case, although the receiver was in the engine 

 room, surrounded by tons of steel, messages were 

 recorded accurately. Afterward Marconi signaled 

 from Needles Hotel, Alum Bay, Isle of Wight, to 

 Swanage on the mainland, 17- miles distant, the 

 receiver being on board a moving steamer, and the 

 weather being stormy. After this feat regular 

 communication was kept up between Alum Bay 

 and Bournemouth, 14 miles, and the second sta- 

 tion was removed in September, 1898, to Poole, 18 

 miles away. An average of 1,000 words daily have 

 been transmitted between these points. Stations 

 intended for permanent service have been estab- 

 lished also at Durlston Castle and elsewhere. 



In May, 1898, signals were sent between Bally- 

 castle and Rathlin island, in the north of Ireland, 

 ?i miles, and in July the progress of a yacht race 

 (the Kingstown regatta) was reported for the 

 41 Dublin Express " from a steamer that followed 

 the yachts, whose distance from the receiving sta- 

 tion on land at Kingstown was sometimes as great 

 as 10 miles. The vertical wire on the steamer was 

 75 feet high, and was attached to the mast. Later, 

 in August, messages were sent from the Prince of 

 Wales's yacht " Osborne " in Cowes Bay to the Queen 

 at Osborne House. In one case communication was 

 kept up until the yacht was 7 miles away. During 

 the winter of 1898 messages were sent regularly 

 between South Foreland lighthouse and the light- 

 ship " East Goodwin," 12 miles distant. The sys- 

 tem worked admirably, as reported by Signor Mar- 

 coni, through the severest winter storms. On March 

 27, 1899, messages were sent across the English 

 Channel from the vicinity of Boulogne, France, to 

 the South Foreland, England, a distance of 32 miles. 

 The Morse code was used, and the results are said to 

 have been satisfactory. 



Dr. Slaby. of Charlottenburg, Germany (see " Cen- 

 tury Magazine," April), has sent signals by space 

 telegraphy on the Marconi system between Scho'ne- 

 berg, near Berlin, and Rangsdorf, a distance of 21 

 kilometres (13 miles), assisted by the German army 

 balloon corps. Balloons anchored at the two sta- 

 tions held lengths of copper wire 250 metres long, 

 which hung to the ground. Balloons or kites can 

 thus be used in space telegraphy either by land or 

 by sea. 



Dr. Strecker, in a paper before the Berlin Elek- 

 trotechnischer Verein, describes experiments on the 

 use of long horizontal wires in place of vertical 

 ones. Dr. Slaby, by using wires 100 metres long, 

 2 metres above the surface of the ground, had trans- 

 mitted signals 3 kilometres. In Strecker's experi- 

 ments, the wires connected to the transmitting and 

 receiving apparatus were also 100 metres long and 

 parallel to one another, but the distance between 

 them was 5.7 kilometres. Bronze wire, supported 

 on ordinary telegraph poles and insulators, was 

 employed. In spite of wet weather the experi- 

 ments,' which were continued for some weeks, were 

 on the whole successful, distinct signals being re- 

 ceived ; but the Morse signals were long, and t he 



transmission was therefore very slow. Modifica- 

 tions made by putting the coherer in tin- middl.- 

 instead of at the end of the line, and iiu-n-sising 

 the length of the receiving line to 300 met res, did 

 not cause marked improvement. Strecker con- 

 cludes that employing ordinary telegraph stores, 

 and horizontal in place of vertical wires, signals 

 can be transmitted through a distance over 50 

 times the length of the wires. 



Uses and Limitations. The limitations of 

 space telegraphy are thus stated by Rollo Apple- 

 yard in "Nature," Jan. 12, 1899: 



" It is very generally admitted that space tele- 

 graphy will replace metallic-circuit systems only 

 under conditions where metallic circuits are ini- 



Eracticable. The fact that metallic circuits have 

 een laid over the Andes may be taken as proof 

 that there are remarkably few land areas that can 

 not be spanned by wires. For cominunifation be- 

 tween fixed points on rough coasts a wire suitably 

 protected is still the right and the best thing. . . . 

 The great advantage of a metallic-circuit system is 

 the consequent privacy of the messages, the sim- 

 plicity of the apparatus, the speed of transmission, 

 and the possibility the system offers for working by 

 telephone, and in other ways avoiding the expense 

 of skilled operators. Space telegraphy is at pres- 

 ent limited to comparatively short distances, and its 

 usefulness is confined to spanning estuaries, skirt- 

 ing seaboards, and for such purposes as that to 

 which it was applied by Mr. Preece between Oban 

 and Mull in 1895. But, except in rare instances, it 

 is only likely to replace submarine cables between 

 moored vessels and the shore, e. g. between light- 

 ships and the coastguard stations. The point of 

 failure in submarine-cable communication thus 

 happens to coincide with the point of favor of 

 space telegraphy. The present object of those 

 working at space telegraphy should therefore be to 

 supplement the cable system of coast telegraphs, 

 so that all the light vessels and lighthouses of our 

 coasts may be brought into communication with 

 one another and with the lifeboat stations." 



One of the weak points of space telegraphy, as 

 pointed out by A. V. Abbott in a recent lecture 

 (" Western Electrician," Chicago, December) is that 

 there is necessarily a waste of energy, the sending 

 of a message to a distance of one mile involving the 

 filling with electric waves of a sphere two miles in 

 diameter, of which the transmitting instrument is 

 the center and the receiver but a point on the sur- 

 face. " Applied to transmission over long dis- 

 tances, such an expenditure of energy becomes 

 commercially appalling." In ordinary telegraphy, 

 although the actual energy is now believed to 

 travel through space, it is directed by the wire. 

 For this reason the use of the new method must 

 probably remain restricted to cases where direct 

 wire connection is impossible or impracticable. In 

 an effort to overcome this objection. Prof. Xickler, of 

 P.riinn. Germany (" Elektrotechnische Rundschau," 

 Nov. 21, 1898) has devised a method of using a beam 

 of ultraviolet light to actuate his receiving instru- 

 ment. He employs a powerful arc lamp as his 

 transmitter, anng a screen of glass to produce in- 

 termittent flashes of the ultraviolet beam, which 

 embody themselves as dot and dash signals on his 

 receiver. The receiver is an air gan in a circuit 

 containing an induction coil regulated to an electro- 

 motive force just below the sparking point at the 

 air gap. As Hertz showed, a beam of ultraviolet 

 light falling on the cathode of a strained air gap, 

 near its breaking-down point, provoke* a discharge, 

 Zickler started by producing this effect over a dis- 

 tance of two metres. Then, by improving the 

 shape and material of his electrodes, and inclosing 

 them in a chamber of compressed air. he was able 



