in Magnetism and Electricity. 105 



tors, would not make the shortest length of the same wire red- 

 hot (176, 177). 



187. That the increase of discharge from the2J-inch machine 

 into the sea above that which was transmitted into the canal 

 from the same electromotor, under like conditions, should be 

 attended by a corresponding diminution of electrodynamic effect 

 at the distant point C, D, was only what might have been ex- 

 pected from the results already obtained in the canal : thus, 

 when the current from this machine was transmitted through 

 the conductors extended in the sea, the amount of current ar- 

 riving at C, D would only make f of an inch of the thin wire 

 red-hot ; whereas when the conductors were extended in the 

 canal, the current from the same machine would melt, at C, D, 

 3 inches of this same wire. When, however, a single Grove's 

 cell was connected with the conductors extended in the sea, the 

 current arriving at the distant point was, owing to its compara- 

 tively low intensity, so little diminished that it would make ^ an 

 inch of the thin wire red-hot. 



188. The similarity of the results exhibited at the distant 

 ends of the conductors when extended in the sea and in the 

 canal with those obtained with the double coil immersed in the 

 tub of salt water, affords another illustration of the dependence 

 of the phenomenon of the earth's conductivity upon the electro- 

 chemical properties of the liquids in contact with the conductors, 

 and leads me to think that currents of electricity of great quan- 

 tity, but of an intensity below that which is required to effect 

 the electrolyzation of the liquid in which the conductors are 

 submerged, might be transmitted to considerable distances with- 

 out the necessity of surrounding the conductors with an insu- 

 lating envelope. How far it may be practicable, under the most 

 favourable circumstances, to transmit to distant places electric 

 currents sufficiently powerful to be made available for any useful 

 purpose under conditions so anomalous as those above men- 

 tioned, it is impossible to say without further experiments with 

 conductors of much greater length than those which I have em- 

 ployed. I will, however, just mention that in a series of expe- 

 riments made with two lengths of the same copper rope as that 

 used in the preceding experiments, each 750 feet long, extended 

 in the canal, while a marked diminution of electrodynamic effects 

 was observed at C, D when currents of high tension were trans- 

 mitted through these conductors, yet currents of low tension 

 arrived at C, D with but little diminution of their primitive in- 

 tensity. Even with a current of so great an intensity as that 

 from the 10-inch intensity-armature it was very interesting to 

 witness the powerful electrodynamic effects produced at the ends 

 C, D of the naked conductors ; for after the current had passed 



