224 POPULAR LECTURES AND ADDRESSES. 



speaking of. I would just briefly say that the 

 kind of observation which would be of value for 

 the scientific problem is to observe the indication 

 of an electrometer at each end of a telegraph line 

 at any time, whether during a magnetic storm or 

 not, and at any time of the night or day. If the 

 line be worked with a condenser at each end, this 

 observation can be made without in the slightest 

 degree influencing, and therefore without in the 

 slightest degree disturbing, the practical work 

 throughout the line. Put on an electrometer in 

 direct connection with the line, connect the outside 

 of the electrometer with a proper earth connection, 

 and it may be observed quite irrespectively of the 

 signalling ; when the signalling is done, as it very 

 frequently is at submarine lines, with a condenser 

 at each end. The scientific observation will be 

 disturbed undoubtedly, and considerably disturbed, 

 by the sending of messages ; but the disturbance 

 is only transient, and in the very pause at the end 

 of a word there will be a sufficiently near approach 

 to steadiness in the potential at the end of the 

 win- connected with the electrometer to allow a 



