444 PHltOSOPHICAL TRANSACTIONS. [aNNO 1747-8. 



the like trials with the places a and c, the commotions were perceptible from a 

 to c ; a distance not less than 2800 feet by land, and near 8000 by water. 



To execute this, to the former wire, which was already conducted to b, 

 another was added, which there crossed the river without touching the water; 

 and reached almost to c, where the first of a line of gentlemen held as before 

 the wire in one hand, and the last dipped the iron into the water. The wire 

 from the machine to a was as before. Its effects were plainly though but faintly 

 perceived each time by some of the observers, but never by them all. The elec- 

 trical commotion was always felt by that observer, who held the extremity of the 

 wire, but never by him who held the iron rod in the water. It was in one expe- 

 riment felt by the observer who held the wire, not felt by the next who held the 

 hand of the former, and yet plainly perceived by the third who joined the second. 

 Those who did not themselves feel the electrical commotion here, did as at b, 

 see the involuntary motions of those who did. The observers at a felt the shocks 

 in the same degree, whether the other obsei-vers were stationed at b or c. 



This experiment further demonstrates the distance to which the electrical power 

 may be conveyed : but the same difficulty occurs here as in the last, viz. whether 

 the circuit was completed by the water of the river, or by the ground which 

 was wet? 



To resolve this doubt then, the gentlemen met again July 28, 1 747 : when 

 the electrical commotion was first tried from a to b beforementioned, the iron 

 wire in its whole length being supported, without any where touching the ground, 

 by dry sticks placed at proper intervals, of about 3 feet in height. The observers 

 both at A and b stood on originally-electrics, and, on the signal, dipped their 

 iron rods into the water. On discharging the phial, which was several times 

 done, they were both very much shocked, much more so than when the con- 

 ducting wire lay on the ground, and the observers stood on it, as in the former 

 experiments. The same experiment was tried with the observer at a, instead of 

 the iron rod, dipping a narrow slab of Portland stone into the water of about 3-i- 

 feet in length; when the shock was felt, but not so severe as through the iron 

 rod. This demonstrated, as was before suggested, why the electrical commotion 

 was not felt stronger by the observers on the western shore of Westminster 

 bridge, viz. that Portland stone standing in water will conduct electricity very 

 considerably. 



The gentlemen then tried what would be the efi^ect, if the observer at b stood 

 on a cake of wax holding the wire as before, and touched the ground of the 

 meadow with his iron rod at least 150 feet from the water; and if the observer 

 usually placed near the river at a, had his wire carried 150 feet over the river as 

 the former, stood on an originally-electric, and touched the ground with his iron 

 rod. On the explosion of the charged phial, which was several times done, both 



