260 INDO-EUROPEAN LINE. 



circumstance that the two wires, especially in dry 

 weather, interfered with one another. This showed 

 itself first in Persia, where the chief engineer of the 

 Berlin firm, Herr Frischen. was occupied in arranging 

 the telegraph service. With the very dry weather 

 prevailing there the two wires were entirely insulated 

 from one another and from the earth, and nevertheless 

 correct Morse writing was received on both receiving 

 instruments of the distant station, when a message was 

 sent on one of the two lines. As the receiving apparatus 

 of the second line at the sending station showed 

 reversed writing, the cause of the disturbances could 

 not but be in the electrostatic charge of the side 

 line, for the currents dynamically induced in it should 

 have given reversed writing at both ends of the second 

 line. This was proved by a series of experiments, 

 which Herr Frischen made in Teheran on my wired 

 instruction. After the cause of the disturbance was 

 ascertained, it could be rendered innocuous by suitable 

 precautions. 



This leads me to observe that this double cause 

 of the induced currents arising in neighbouring wires 



O o O 



occasions in the working of telephones many dis- 

 turbances hitherto not altogether intelligible, and still 

 needs thorough investigation. I have subsequently 

 had an opportunity, when my firm laid a seven- 

 cored land cable, to institute an instructive experi- 

 ment in reference to this phenomenon. With the 

 permission of the imperial telegraph administration 

 one of the seven conductors of the cable from Darm- 



