94 OVERHEAD EISENACH-FRANKFORT LINE. 



between the government of Prussia and the adminis- 

 tration of the empire after the restoration of order 

 in Berlin had become considerably acuter in conse- 

 quence of the entrance of the army returning from 

 Schleswig-Holstein. I only succeeded in executing my 

 task by obtaining an open order from the vicar-general 

 of the empire Archduke John. Technical difficulties 

 also made their appearance. The line was constructed 

 of copper wire, as suitable iron wires were not then to 

 be had in Germany, and moreover were still regarded 

 with a certain mistrust. The unfortunate experiences 

 which we had had the foregoing year in the case of 

 the Berlin-Potsdam line, which despite the application 

 of all sorts of insulating media proved so badly insu- 

 lated in rainy weather that the proper service of the 

 apparatus was constantly disturbed, had led me to 

 make use of bell-shaped insulators of porcelain. These 

 possessed the great advantage that the inner surface 

 of the bell always remained dry even in rainy weather, 

 whereby the insulation was secured under all circum- 

 stances. In fact I succeeded in this way in producing 

 an almost perfect insulation. Unfortunately I did not 

 then think it necessary to solder the copper wire, 

 close coiling seeming to me sufficient. This afterwards 

 turned out to be an error. In calm weather the 

 apparatus acted very well, but with a strong wind the 

 resistance of the conductor was so remarkably variable 

 that the apparatus refused to work. Only subsequent 

 soldering of all the joints put an end to this trouble. 

 The atmospheric electricity proved also very 



