132 



NA TURE 



[December it, 1902 



for example, that of the Marconi Company, the former pur- 

 pose is almost as much in view as the latter. In the former 

 case, there can be no question but that absolute syntpnis- 

 ation is necessary ; in the latter, it is less important and 

 even in some respects undesirable, but, on the other hand, it 

 is essential that the different systems should work together 

 so that any ship should be able to signal to any station. 

 It would be a great misfortune if this principle is lost sight 

 of in the rivalry between competing methods and if we 

 thereby lose what seems to be in reality the greatest 

 benefit wireless telegraphy can confer, the increase of the 

 =afety and convenience of travelling by sea. This is, we 

 think, the most urgent problem that wireless telegraphy 

 presents to-day, and we trust that it will find a really satis- 

 factory solution at the coming Berlin Conference. 



The attempts which have been made at syntonisation 

 are, indeed, far from encouraging. It is true that almost 

 every inventor claims that he has solved the problem, but 

 all the experiments that have been quoted are open to 

 criticism. It is important to recognise what a successful 

 solution really means ; it is not sufficient to demonstrate, 

 as has been done many times, that two messages can be 

 transmitted or received at the same time by the same 

 installation without interference ; that, in short, duplex- 

 ing is possible : this is a great step, no doubt, but to solve 

 the problem it is necessary that the tuned transmitter shall 

 affect no other receivers than those syntonised with it, and 

 that the tuned receiver shall respond only to the proper 

 waves ; this, it will be seen, is a requirement much harder 

 to satisfy. As an example, showing how far existing 

 practice is from satisfying these conditions, we may quote 

 the case of the recent long-distance work done by the 

 Marconi Company. Mr. Marconi, it will be remembered, 

 has several times claimed to have solved the problem of 

 syntonisation, and, confident of having done so, issued a 

 challenge last February to Sir W. Preece or Sir O. Lodge 

 to intercept any of his messages, offering to put a station, 

 in the neighbourhood of his I'oldhu station, at their service. 

 This challenge has been answered in a conclusive manner 

 •during the past month by Mr. Nevil Maskelyne, who 

 showed that the installation which he was working at 

 Pqrtcurnow had been receiving the messages sent to the 

 Carlo Alberto on her recent cruise from England to Italy 

 (see the Electrician, vol. 1., pp. 22 and 105). It is 

 clear, therefore, that, with no special preparation on 

 either side, it is possible to tap the signals that are being 

 sent by the Marconi Company over long distances, and 

 in face of this the claims to a real solution of the syntonis- 

 ation problem fall to the ground. We doubt whether any 

 other system would stand the same test. 



But if on this side the outlook is somewhat dispiriting, 

 in other directions matters are more encouraging. This 

 year has witnessed the remarkable achievements by the 

 Marconi Company in long-distance work. It has been 

 shown that it is possible to signal across the Atlantic, a 

 distance of more than 2000 miles over water ; and in the 

 cruise of the Carlo Alberto signals were transmitted a 

 distance of 750 miles over land and water. To cover 

 these great distances, the power used at the transmitting 

 station has to be correspondingly great ; in consequence, 

 the signalling was only from Poldhu to the ship and not 

 in the reverse direction. The importance of these experi- 

 ments, however, lies rather in the conclusive demonstra- 

 tion of the fact that it is only a question of providing 

 sufficient power to signal over any distance, however 

 great, and therefore no fears need be entertained of the 

 utility of the wireless telegraph being limited by consider- 

 ations of distance. No other experimenter has attained 

 such success in long-distance work as Mr. Marconi, but 

 no other experimenter has used such large power for 

 transmission. Unfortunately, sufficient particulars are 

 not available to enable a comparison to be made between 

 the distances attained with different systems using the 

 same amount of power ; this is a point on which the 



NO. 1728, VOL. 67] 



publication of trustworthy data would be of the highest 

 value. An interesting phenomenon brought out by Mr. 

 Marconi's long-distance work is the effect produced by 

 daylight on transmission. It is found that the signals 

 carry much further during the night {i.e. night at the 

 transmitting station), the result being due, it is suggested 

 to the discharging effect of sunlight on the aerial wire 

 (see Nature, vol. lxvi. p. 385). 



With reference to long-distance work, the interesting 

 experiments of M. Guarini with an automatic repeater 

 may be quoted. This inventor designed an apparatus 

 which should pick up a message received from one station, 

 A, and pass it on to a second station, B, which was out of 

 the range of the signals transmitted direct from A. The 

 principle of this apparatus will be understood from the 

 accompanying diagram (Fig. 1), in which, for the sake of 

 clearness, only the essential circuits are shown. The 

 aerial wire A at the repeating station is connected 

 through the contact 1 of the relay Rj and through the 

 primary of a transformer T to earth ; it is also connected 

 through the spark gap s to earth. The coherer is con- 

 nected in series with the secondary of T and a condenser. 

 When a signal is received, the resistance of the coherer is 

 broken down, and the battery Bj sends a current through 

 it and the relay R 2l thus closing at the contact 3 the 



T °i 



\Eartk 



Fig. 1. — Diagram of Circuits in Guarini's Repeater. 



circuit of the relay R t . The contact arm of Rj swings 

 over to 2, thus disconnecting the aerial from the receiving 

 circuit and closing the primary of the induction coil T 2 , 

 thereby causing a spark to pass across the gap, which 

 means that the signal is sent out again from the aerial A. 

 The coherer being tapped back, the various circuits are 

 opened, and the arm of k, returns to its original position 

 and so is ready to receive the next signal. Experiments 

 were carried out between Antwerp and Brussels (42 km.), 

 the repeating station being at Malines, about half-way 

 between the two ; the results were promising, though the 

 repeater did not prove absolutely trustworthy. 



We may now turn from the consideration of the results 

 achieved to the apparatus that has been used. In the 

 transmitting apparatus, attention has been chiefly devoted 

 to devising means of generating oscillations of definite 

 wave-length. None of these call for special comment. 

 In some cases, for obtaining the spark, alternating-current 

 generators have been employed in connection with step- 

 up transformers instead of induction coils. This is the 

 case in the de Forest system, which, it may be remarked, 

 claims the recordfor speed of forty-eight words per minute ; 

 the alternator generates, at 500 volts, 60 cycles, and this is 

 stepped up to 25,000 volts for sparking ; the signals are 

 formed by interrupting the primary circuit of the trans- 

 former by means of a specially designed key. The diffi- 

 culty of breaking a large current in this way is consider- 



