Dec. 28, 1876] 



NATURE 



183 



which could be disturbed by the operator at the other 

 station. This arrangement is shown in Fig. 5. 



Here, as will be seen, the batteries are equal and are 

 constantly connected to the line, so that their like poles 

 oppose each other through the differential coils of the 

 receiving instrument and the line. Thus the balance is 

 maintained. But when at station s, for instance, contact 

 is made with earth by the keys K, the battery B will be 

 cut off from the line, and the current from station s', no 

 longer opposed, will make a signal on the instrument 

 there. Winter's method was tried with some success in 

 India. Up to this time experiments had been for the 

 most part confined to land-lines. 



Attention now began to be turned to submarine cables, 

 and Winter proposed the use of secondary batteries, made 

 of plates of one metal (as lead) immersed in a single 

 fluid (as sulphuric acid), in order to provide the large 

 electric induction necessary to the artificial line, or by 

 application in some particular way to the receiving in- 

 strument, so as to counterfeit the induction " kicks." 



Stearns, also, in the same year, took out further patents 

 principally for the purpose of extending his system to 

 cable work. For example, he patented combinations of 



Rl 



condensers and resistance coils to represent an artificial 



R 1 



SF 



R 



"S 



B 



1 K 



w 



Fro 4. 



cable. This, however, had been done "as early as 1862 



% \ 



by Varley, for the purpose of making an imitation cable 

 for use as a " test " circuit. Varley distributed his con 

 densers along his resistance circuit in the manner shown 

 in Fig. 6, so as to approximate to the uniform distribu- 

 tion of resistance and capacity in a submarine cable ; 

 but Stearns confined himself to attaching his condensers 

 all at one point of his rheostat, and modifying their 

 charges in various ways by means of resistance coils. 

 Stearns also proposed various additional arrangements 

 for superimposing " kicks " on the receiving instrument 

 which should counterbalance the inductive " kicks " 

 known to be very violent and difficult to obviate on sub- 

 marine cables. He also describes a method of construct- 

 ing his condensers in the form of a submarine cable ; 



Fig. S- 



)le and, apparently for the purpose of economising material, 

 m- he further proposes to employ Gintl's original plan of two 

 vn 



'U- J^^'^^^^J—^^-^^^r^^^-^ 



Catutnisers 



Fig. 6. 



batteries ; but in this case the stronger battery would be 

 used to charge the artificial line, so that, with less capacity 



Conducting Strip 



. .T/isuldloY* 



m^ > to Earth 



Indue tin a Plate 



bo TJarth 



Tig. 7. 



than the actual line, its inductive "kick" might be made 

 equivalent to that of the latter. In fact, Stearns and 

 Winter appear, naturally enough, to have striven rather 

 to effect the duplex balance by some device or by an 

 artificial line approximately similar, instead of aiming at 

 one approximately equal to the actual cable. 



In 1874 Mr. Louis Schwendler, of Calcutta, patented a 

 system founded on the Wheatstone balance principle, and 

 applicable to submarine cables by the use of resistance 

 coils and condensers, or of a cable itself as an artificial 



line ; but Schwendler's system is only novel for the ratios 

 between the resistances of the balance which it lays down. 

 The best results are said to be given when the resistances 

 r', R and w, Fig. 3, are each one-half of the resistance of 

 the line, and r is made equal to one-sixth of the resist- 

 ance of the line. 



The first successful trials in submarine duplex that we 

 hear of are mentioned in the Journal of tJie Society of 

 Telei::;raph Engineers for 1874. From this it appears that 

 Messrs. De Sauty and Harwood, both of the Eastern 



