554 PHILOSOPHICAL TRANSACTIONS. [aNNO 1748. 



Royal Society; also Dr. Bevis, and Mr. Grischow, jun. a member of the Royal 

 Academy of Sciences at Berlin. 



It was agreed to make the electrical circuit of 2 miles ; in the middle of which 

 an observer was to take in each hand one of the extremities of a wire, which 

 was a mile in length. These wires were to be so disposed, that this observer 

 being placed on the floor of the room near the electrical machine, the other ob- 

 servers might be able in the same view to see the explosion of the charged phial, 

 and the observer holding the wire; and might take notice of the time lapsed be- 

 tween the discharging the phial and the convulsive motions of the arms of the 

 observer in consequence of it; as this time would show the velocity of electricity, 

 through a space equal to the length of the wire between the coated phial and the 

 observer. 



The electrifying machine was placed in the same house as it was last year. We 

 then found ourselves, says Mr. W. greatly embarrassed by the wire's being con- 

 ducted by the side of the road, which we were compelled to, on account of the 

 space necessary for the measuring of sound; but so great a distance from the 

 machine was not now wanted, though the circuit through the wire was intended 

 to be at least 2 miles. We had discovered, by our former experiments, that the 

 only caution now necessary was, that the wires conducted on dry sticks should 

 not touch the ground, nor each other, nor any non-electric, in a considerable 

 degree, in any part of their length ; if they did not touch each other, the returns 

 of the wire, be they ever so frequent, imported little, as the wire had been found 

 to conduct electricity so much better than the sticks. It was therefore thought 

 proper to place these sticks in a field 50 yards distant from the machine. The 

 length of this field being 1 1 chains, or 7^6 feet, 8 returns of the wire from the 

 top to the bottom of the field, made somewhat more than a mile, and 1 6 returns 

 more than 2 miles, the quantity of wire intended for the electricity to pass 

 through to make the experiment. 



We had found last year, that on discharging the electrified phials, if 2 ob- 

 servers made their bodies part of the circuit, one of which grasped the leaden 

 coating of the phial in one hand, and held in his other one extremity of the 

 conducting wire ; and if the other observer held the other extremity of the con- 

 ducting wire in one hand, and took in his other the short iron rod with which 

 the explosion was made ; on this explosion, they were both shocked in the same 

 instant, which was that of the explosion of the phial. If therefore an observer 

 making his body part of the circuit, was shocked in the instant of the explosion 

 of the charged phial in the middle of the wire, no doubt would remain of the 

 velocity of electricity being instantaneous through the length of that whole wire. 

 But if, on the contrary, the time between making the explosion, and seeing the 

 convulsions in the arms of the observer holding the conducting wires, was great 



