Associated cases of Current and Static Effects. 207 



maximum, but always continuous. If the action of the contact 

 key was less rapid, then alternate thickening and attenuations 

 appeared in the o record ; and if the introductions of the electric 

 current at the one end of the earth wire were at still longer 

 intervals, the records of action at the other end became entirely 

 separated from each other. All showing most beautifully how 

 the individual current or wave, once introduced into the wire, 

 and never ceasing to go onward in its course, could be aflFected 

 in its intensity, its time and other circumstances, by its partial 

 occupation in static induction. 



By other arrangements of the pens n and o, the near end of 

 the subterraneous wire could be connected with the earth imme- 

 diately after separation from the battery; and then the back 

 flow of the electi'icity, and the time and manner thereof, were 

 beautifully recorded ; but I must refrain from detailing results 

 which have already been described in principle. 



Many variations of these expei'iments have been made and 

 may be devised. Thus the ends of the insulated batteiy have 

 been attached to the ends of the long subterraneous wire, and 

 then the two halves of the wire have given back opposite return 

 currents when connected with the earth. In such a case the 

 wire is positive and negative at the two extremities, being per- 

 manently sustained by its length and the battery, in the same 

 condition which is given to the short wire for a moment by the 

 Leyden discharge (p. 203) ; or, for an extreme but like case, to a 

 filament of shell-lac having its extremities charged positive and 

 negative. Coulomb pointed out the difierence of long and short 

 as to the insulating or conducting power of such filaments, and 

 like difference occurs with long and short metal wires. 



The character of the phfenomeua described in this report in- 

 duces me to refer to the terms intensity and quantity as applied 

 to electricity, terms which I have had such frequent occasion to 

 employ. These terms, or equivalents for them, cannot be dis- 

 pensed with by those who study both the static and the dynamic 

 relations of electricity ; every current where there is resistance 

 has the static clement and induction involved in it, whilst every 

 case of insulation has more or less of the dynamic clement and 

 conduction ; and we have seen that with the same voltaic source, 

 the same current in the same length of the same wire gives a 

 diffierent result as the intensity is made to vary, with variations of 

 the induction around the wire. The idea of intensity, or the 

 power of overcoming resistance, is as necessary to that of elec- 

 tricity, cither static or current, as the idea of pressure is to steam 

 in a boiler, or to air passing througli apertures or tubes; and we 

 must liavc language competent to express these conditions and 

 these ideas. Furthermore, I have never found either of these 



