VOL. XLV.^ PHILOSOPHICAX- TRANSACTIONS. 451 



conducted, the electrical commotions from the charged phial have been very con- 

 siderable only, when the observers at the extremities of the wire have touched 

 some substance readily conducting electricity with some part of their bodies. 



'2. That the electrical commotion is always felt most sensibly in those parts of 

 the bodies of the observers, which are between the conducting wires, and the 

 nearest and the most non-electric substance; or in other words, so much of their 

 bodies as comes within the electrical circuit. 



3. That on these considerations we infer, that the electrical power is conducted 

 between these observers by any non-electric substances, which happen to be 

 situated between them, and contribute to form the electrical circuit. 



4. That the electrical commotion has been perceptible to two or more observers 

 at considerable distances from each other, even as far as 2 miles. 



5. That when the observers have been shocked at the end of 2 miles of wire, 

 we infer that the electrical circuit is 4 miles, viz. 2 miles of wire, and the space 

 of 2 miles of the non-electric matter between the observers, whether it be water, 

 earth, or both. 



§. That the electrical commotion is equally strong, whether it is conducted by 

 water or dry ground. 



7. That if the wires, between the electrifying machine and the observers, are 

 conducted on dry sticks, or other substances non-electric in a slight degree only, 

 the effects of the electrical power are much greater than when the wires in their 

 progress touch the ground, or moist vegetables, or other substances in a gi-eat 

 degree non-electric. 



8. That by comparing the respective velocities of electricity and sound; that 

 of electricity, in any of the distances yet experienced, is nearly instantaneous. 



The gentlemen concerned were still desirous, if possible, of ascertaining the ab- 

 solute velocity of electricity at a certain distance; because, though last year in 

 measuring the respective velocities of electricity and sound, the time of its pro- 

 gress was found to be very little, yet they were desirous of knowing, small as 

 that time was, whether it was measureable; and Mr. W. had thought of an 

 other method for this purpose. 



Accordingly, Aug. 5, 1748, there met at Shooter's Hill for this purpose the 

 president of the Royal Society, and several other gentlemen : when 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 electrifying machine, the other observers might be able in 

 the same view to see the explosion of the charged phial and the observer holding 

 the wires, and might take notice of the time lapsed between the discharging the 

 phial and the convulsive motions of the arms of the observer in consequence of 



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