Associated cases of Current and Static Effects. 201 



of the coils of wire. I understand that 100 miles of wire, 

 stretched in a line through the air so as to have its whole extent 

 opposed to earth, is equally inefl&cient in showing the eflfectSj 

 and there it must be the distance of the inductric and inducteous 

 surfaces (1483.), combined with the lower specific inductive 

 capacity of air, as compared with gutta percha, which causes the 

 negative result. The phfenomeua altogether offer a beautiful 

 case of the identity of static and dynamic electricity. The whole 

 power of a considerable battery may in this way be worked off 

 in separate portions, and measured out in units of static force, 

 and yet be employed aftei-wards for any or every purpose of vol- 

 taic electricity. 



I now proceed to further consequences of associated static and 

 dynamic effects. Wires covered with gutta percha and then 

 inclosed in tubes of lead or of iron, or buried in the earth, or 

 sunk in the sea, exhibit the same phsenomeua as those described, 

 the like static inductive action being in all these cases permitted 

 by the conditions. Such subterraneous wires exist between 

 London and Manchester ; and when they are all connected 

 together so as to make one series, offer above 1500 miles ; which, 

 as the duplications return to London, can be observed by one 

 experimenter at intervals of about 400 miles, by the introduction 

 of galvanometers at these returns. This wire, or the half or fourth 

 of it, presented all the pheenomena already described ; the only 

 difference was, that as the iusulation was not so perfect, the 

 charged condition fell more rapidly. Consider 750 miles of the 

 wire in one length, a galvanometer a being at the beginning of 

 the wire, a second galvanometer b in the middle, and a third c 

 at the end; these three galvanometers being in the room with 

 the experimenter, and the third c perfectly connected with the 

 earth. On bringing the pole of the battei-y into contact with 

 the wire through the galvanometer a, that instrument was in- 

 stantly affected ; after a sensible time b was affected, and after a 

 still longer time c: when the whole 1500 miles were included, 

 it required two seconds for the electric stream to reach tlie last 

 instrument. Again ; all the instruments being deflected (of 

 course not equally, because of the electric leakage along the line), 

 if the battery were cut off at a, that instrument instantly fell to 

 zero ; but b did not fall until a little while after ; and c only 

 after a still longer interval, — a current flowing on to the end of 

 the wire whilst there was none flowing in at the beginning. 

 Again ; by a short touch of the battery pole against a, it could 

 be deflected and could fall back into its neutral condition before 

 the electric power had reached b ; which in its turn would be 

 for an instant affected, and then left neutral Ijefore the power 

 had reached c ; a wave of force having been sent into the wire 



Phil. Mug. S. 4. Vol. 7. No. 44. March 1854. P 



