( 526 ) 



simple means and connected to it often, by introducing a resistance 

 of 100 or 1000 Ohm, a measurement, though a rough one, of the 

 total resistance of the whole circuit. 



The results generally showed a mutual correspondence, only for 

 longer lines a distinct loss by defective isolation was often discernible. 



For the earth-current this loss by defective isolation is of not much 

 consequence; for, if two points lying at a distance Z from each other 

 with potentials P and P -}- L^, are connected by a wire the potential 

 will vary along that wire proportional to the distance of P to 

 P -\~ Lp and will be in a point between the two, say at 1/a of the 



distance, P -\ — ~. But there the potential of the earth will also be 

 a 



P -\ — - if that earth potential likewise varies proportionally to the 



a 



distance (which we shall suppose to be true at first computation). There 

 will thus be no difference of potential between line and point of 

 contact with the ground, neithei- loss of current.^) 



However there is loss of current, when I switch on a cell, thus 

 when I generate a drop of potential along the wire, that does 

 not at all run parallel to the earth potential. 



This explains that the image of the earth-current rose and fell so 

 regularly with the magnetic component, whilst so often a great loss 

 by defective isolation took place on the line, so that the determination 

 of the values of the scale division by means of inserting a cell gave 

 abnormal values. 



When, however, an investigation must be made of the regular 

 or non-regular increase of the earth-potential with the distance, then 

 this loss by defective isolation is disturbing. That is why the registering 

 with the continuous connection Batavia — Makassar shed no light upon 

 the subject. 



Infiuence of the material of the line. 



1 could experiment accurately on the possibility of the influence 

 of the material of the conductive wire on amplitude and phase of 

 the earth-current by registering simultaneously the currents between 

 Cheribon and Batavia, resp. through the copper telephone wire and 

 the iron telegraph one. 



1) If we suppose the earth-current to form a closed circuit passing round the 

 earth and our wire to have contact with it in three points viz. at the two end 

 stations and the point of contact, there is a distribution of current according 

 to Wheatstone and the contact is the bridge of Wheatstone. 



