90 MANUFACTURE OF GUTTA-PERCHA INSULATORS. 



demand for gutta-percha, the best insulating sort was 

 soon out of the market. 



To cope with this impediment to the rapid pro- 

 gress required of the work it was resolved to make 

 use of the recent English invention of vulcanizing the 

 gutta-percha, i. e. intimately mixing it with sulphur, 

 whereby even with inferior kinds of gutta-percha the 

 insulation of the condiictors as well as their power 

 of resisting external injuries was increased. Unfortuna- 

 tely the vulcanization turned out afterwards a mistake, 

 as the sulphur combined with the copper of the con- 

 ductor and thereby also the adjacent layers of gutta- 

 percha became gradually coppery and capable of con- 

 duction. To this circumstance it was mainly ascribable 

 that the wires, though perfectly insulated at the time 

 of their being laid down, had after a few months 

 already lost a part of their insulation. 



Particular care was taken in testing the wires in 

 the factory. Halske manufactured for this purpose 

 galvanometers which far excelled in sensitiveness all 

 known up to that time. In testings with these sensitive 

 galvanometers I observed for the first time in the 

 year 1847 the surprising phenomenon that, even in a 

 perfectly insulated wire lying in water, on interposing 

 a battery a short current occurred, which was suc- 

 ceeded on removal of the battery by an equally strong 

 current in the opposite direction. This was the first 

 observation of the electrostatic charge by galvanic 



o / o 



chains. I w r as at first inclined to see in this a phe- 

 nomenon of polarisation, since at that time the galvano- 



