448 PHILOSOPHICAL TRANSACTIONS. [aNNO 1747-8. 



which the electrifying machine was placed, should be visible at least at one of 

 the stations; and that the space between that house and the stations, through 

 which the wire was conducted, should be very little intersected by hedges, roads, 

 or foot-paths; neither should the wire in this space be subject to be disturbed by 

 the horses or cattle, which were grazing ; nor ought it to touch in its passage the 

 trees, or any other vegetables, which at this season of the year were every where 

 luxuriant. To find a place within a convenient distance of London with these 

 requisites was not very easy; but at last Shooter's Hill was pitched on, as the 

 most convenient. As only one shower of rain had fallen during the preceding 5 

 weeks, the ground could not but be very dry ; and as no water was near, if the 

 electrical commotion was felt by the observers at the stations, it might be safely 

 concluded, that water had no share in conducting it. 



Accordingly, Aug. 14, 1747, they met at Shooter's Hill for this purpose. It 

 was here determined to make 12 explosions of the coated phial, with an observer 

 placed at the 7-mile stone, and another at the Q-mile stone, both standing on 

 wax, and touching the ground with an iron rod. This number of explosions was 

 thought the more necessary, as the observers at these stations were not only to 

 examine whether the electricity would be propagated to so great a distance, but 

 if it were, the observer at the 7-mile stone was by a second watch to take notice of 

 the time lapsed between feeling the electrical commotion, and hearing the report 

 of a gun fired near the machine, as close as might be to the instant of making 

 the explosion ; and therefore, to examine this matter with the requisite exactness, 

 this number of explosions should be made. 



To execute this, the electrifying machine was placed up one pair of stairs in a 

 house on the west side of Shooter's Hill, and a wire from the short iron rod, 

 with which the gun-barrel was touched in making the explosions, was conducted 

 on dry sticks as before into a field near the 7-niile stone. The length of this 

 wire, exclusive of its turnings round the sticks, was a mile, a quarter, and 8 

 poles, or 6732 feet. In great part of this space it was found very difficult to 

 support the wire, on account of our scarcely being able to fix the sticks in the 

 strong gravel there almost without any cover of soil; nor could the wire in some 

 places be prevented from touching the brambles and bushes, nor in one field the 

 ripe barley. 



Another wire was likewise conducted on sticks from the coated phial to the Q- 

 mile stone. In this space, the soil being a strong clay, the wire was very well 

 secured, and in its whole length did not touch the bushes. The length of this 

 wire was 3868 feet. As much as the place, where the observers were stationed 

 in a corn-field, was nearer the machine than the 7-mile stone, so much were the 

 other observers placed beyond the Q-mile stone, that their distance from each 

 other might be 2 miles. The 40 feet of wire in these two measures exceeding 



