Mr. J. N. Hearder on the Atlantic Cable. 37 



ing to the single-fluid hypothesis, of the power of giving out 

 electricity at one end, and taking it in at the other, and if a very 

 long wire have its two ends brought in contact simultaneously 

 with the ends of a voltaic battery or other electro-motor, the 

 first action is an exhausting effort at one end, and a flow of elec- 

 tricity into the opposite end, thus disturbing for a brief instant 

 the normal distribution of the electricity naturally belonging 

 to the wire. However rapidly these effects may pervade the 

 whole length of the wire, there is a time when the ends and the 

 centre will present three diff'erent degrees of electrical condition, 

 the centre being neutral, and the ends respectively plus and 

 minus. Now, suppose contact with the galvanic battery to be 

 made with one end of the wire, only its other end being in con- 

 nection with the earth at a very remote distance, the electrical 

 conditions of the wire will be different. 



If contact be made with the plus end of the battery, a flow of 

 electricity takes place into the wire, producing a wave which 

 gradually flows to the other end, charging the gutta percha in 

 its passage in proportion to the intensity of the current required 

 to overcome the resistance of the wire. That this occupies time, 

 is proved by Mr. Whitehouse's ingenious chronometric test, 

 which registers the time at which the current appears in different 

 portions of the length of the wire. The electrical condition of the 

 wire will in this case be different : the remote end will be neutral 

 until the current reaches it, but the other end will partake of the 

 plus condition of the end of the battery ; and after the current has 

 pervaded the wire, the whole will appear positively charged. If 

 contact with the battery be now broken, and that end of the wire 

 be also made to communicate with the earth, the wire, as far as 

 itself is concerned, instantly becomes neutral, but the charge 

 from the gutta percha now returns to the wire, and flows out at 

 both ends from the centre in opposite directions, giving rise to 

 two currents at the ends of the wire, one at the remote end in the 

 same direction as the first current of the battery, and another 

 out at the near end in opposition to the original current of the 

 battery. 



If this experiment be reversed, and the negative or minus end 

 of the battei-y be brought in contact with the free end of the wire, 

 the other being to earth, a partial exhaustion, as it were, of the 

 electricity natural to the wire takes place, which effect gradually 

 extends to the other end, so that the current is produced :iot by 

 propulsion from the battery, but by exhaustion towards it. As 

 soon as the effect pervades the whole system, therefore, it appears 

 minus or negatively charged, and on breaking contact with the 

 battery and communicating the second end of the wire to earth 

 as before, two opposite currents are again produced, entering the 



