266 



NA TURE 



[April 22, 1909 



A syntonic coherer receiver would, liowever, worli, in con- 

 sequence, no doubt, of the considerable rise of potential 

 which occurred at its terminals through the cumulative 

 effect of resonance. 



The best results over long distances have, however, been 

 obtained by a disc as shown in , Fig. : 14, in which the 

 active surface is not smooth, but consists of a number of 

 knobs or pegs, at the end of which the discharges , take 

 place at regular intervals. In this case, of course, the 

 oscillations are not continuous, but consist of a regular 

 succession of trains of undamped or slightly damped waves. 



In that manner it is possible to cause the groups of 

 oscillations radiated to reproduce a musical note in the 

 receiver, distinguishable in a telephone, and thereby it is 

 easier to differentiate between the signals emanating from 

 the transmitting station and noises caused by atmospheric 

 electrical disturbances. By this method very efficient re- 

 sonance can, moreover, be obtained in appropriately designed 

 receivers. 



A few tests with apparatus based on the principle de- 

 scribed were carried out between Glace Bay and Clifden, 

 and on October 17 of the year 1907 a limited service for 

 Press messages was commenced between Great Britain and 

 America. Difficulties were experienced, however, over the 

 question of rates with the telegraph companies working 

 the land-lines between Glace Bay and the principal towns 

 of Canada and the United States, and at present the strange 



FIC.14. 



anomaly exists that the rates for Press messages on the 

 American land-lines are much cheaper for messages going 

 from England to New York than in the reverse direction. 

 On F'ebruary 3, igo8, this service was extended to ordinary 

 messages between London and Montreal. 



The stations at Clifden and Glace Bay are not complete, 

 and the necessary duplication of the running machinery 

 has not yet been executed, but nevertheless communication 

 across the Atlantic has never been interrupted for more 

 than a few hours since the commencement of commercial 

 working on October 17, 1907. 



There have, however, been several serious interruptions 

 at Clifden, due to the untrustworthiness of the land-lines 

 connecting Clifden to the ordinary telegraph system. On 

 one occasion one of these interruptions lasted from 5.20 p.m. 

 to 10.30 a.m., a duration of seventeen hours, and on 

 another occasion the land telegraph wires were struck by 

 lightning and disabled for twelve hours. There have also 

 been recorded numerous other interruptions of shorter dura- 

 tion, which resulted in delays to private and Press messages. 

 Further delays have also been caused through interruptions 

 on the land-lines connected with the Canadian station. 



During the first months, on account of imperfections in 

 the auxiliary apparatus connected principally with the 

 operating keys and switches, only a fraction of the avail- 



NO. 2061, VOL. So] 



able transmitting power was used. In consequence of this 

 the speed of transmission was slow, and short interruptions, 

 somewhat frequent. Many of these difficulties have now 

 been overcome, and in a few more months, when it should 

 be possible to utilise the full power available, a very;much, 

 greater speed and efficiency is likely to be attained.: ' ; ' , 



Messages can now be transmitted across the Atlantic, by 

 day. as well as by night, but there still exist certain: periods,, 

 fortunately of short duration, when transmission, across the 

 Atlantic is difficult and at times ineffective, .unless an. 

 amount of energy greater than that used during:, what . I. 

 might call normal conditions is employed. 



Thus, in the morning and evening when, due to the 

 difference in longitude, daylight or darkness extends only, 

 part of the way across the Atlantic, the received c signals 

 are weak and sometimes cease altogether. 



It would almost appear as if illuminated space possessed for 

 electric waves a different refractive, index from dark space,' 

 and that in consequence the electric waves may be refracted: 

 and reflected in passing from one; medium to the other.' ,It 

 is therefore probable that these difficulties would not be- 

 experienced in telegraphing over equal distances from north 

 to south, or vice versa, as in this case the passage from 

 daylight to darkness would occur almost simultaneously in 

 the whole of the medium between the two points. 



In the 'same manner a storm area in the path of the 

 signals often brings about a considerable weakening of the 

 received waves, whilst if stormy conditions prevail all the 

 way across the .'\tlantic no interference is noticeable. 

 Electric-wave shadows, like sound shadows, may be formed 

 by the interference of reflected waves with the direct waves, 

 whereby signals may be much less effective or imperceptible 

 in the area of such electric-wave shadow. 



In the same manner as there exist periods when signals 

 across the Atlantic are unusually weak, there exist other 

 conditions, especially at night, which make the signals 

 abnormally strong. Thus on many occasions ships, and 

 stations equipped with apparatus of a normal range of 200 

 miles, have been able to communicate over distances of 

 more than 1000 miles. This occurred recently when a ship 

 in the English Channel was able to correspond with another 

 in the Mediterranean. But the important factor about wire- 

 less telegraphy is that a service established for a certain 

 distance shall be able to maintain trustworthy communica- 

 tion over that distance. 



Long-distance stations are now in course of erection in 

 many parts of the world, the most powerful of all being 

 that of the Italian Government at Coltano, and I have not 

 the slighest doubt but that telegraphy through space will 

 soon be in the position of affording communication between 

 distant countries at cheaper rates than can be obtained by 

 any other means. 



.As to the practicability of wireless telegraphy working 

 over long distances, such as that separating England from 

 .America, there is no longer need for any doubt. Although 

 the stations have been worked for onlv a few hours daily, 

 119,945 vvords of Press and commercial messages had been 

 transmitted across the ocean by this means up to the end 

 of February, 1908, since the service was opened. 



The best judges of a service are those who have made 

 use of it, and amongst newspapers, the chief users have 

 been the Nc\u York Times and the London Times, which 

 have already publicly expressed their opinion of this new 

 method of communication. 



Whether the new telegraphy will or will not injure or 

 displace the cables is still a matter of conjecture, but in 

 my opinion it rests a good deal on what the cables can 

 do in the way of cheaper rates. It is not, as some appear 

 to imagine, either the business or the wish of those con- 

 cerned in the development of wireless telegraphy to injure 

 the cable industry. They are endeavouring at present to 

 demonstrate that the new method is not only valuable for 

 shipping, but that it should be also regarded as a new 

 and cheaper method of communicating with far distant 

 countries. Whatever may be the view as to its short- 

 comings and defects, there can be no doubt but that wire- 

 less telegraohy across the .Atlantic has come to stay, and 

 will not only stay, but continue to advance. 



In seven years the useful range of wireless telegraphy 

 has increased from 200 miles to 2^00 miles. In view of' 



