VOL. XXXVII.] PHILOSOPHICAL TRANSACTIONS. 46I 



be carried to considerable lengths, without touching the line by the tube, — 

 There was taken a line of packthread 231 feet in length ; it was supported on 2 

 cross lines of blue silk, whose distance was near 18 feet: about 4 feet below 

 one of these lines was put up another silk line of the same colour ; to this was 

 tied one end of the packthread ; at the other end the ivory ball hung ; the line 

 was returned over the cross lines 13 times: then the leaf-brass being laid under 

 the ball, on one of the small stands, and the tube excited, the ball attracted 

 and repelled to the height of one of its diameters, which was about an inch and 

 a quarter. 



Mr. Gray found by several trials, that rubbing the tube, and putting it up 

 between the returns of the line in several places, before he went with the tube 

 to the end of the line, much facilitates, and causes the attraction much sooner, 

 than when one stands with the tube, and applies it to the end of the line 

 only. 



August 1, 1730, at Mr. Wheler's was made the following experiment; being 

 an attempt to see how far the electric virtue might be carried forward in a line, 

 without touching the same. — ^This experiment was made by carrying the line 

 out of the great parlour room into the garden, and down the great field before 

 it. The line was supported by 1 5 pair of poles ; each pair had a line of blue 

 silk, tied from one pole to the other, the length about 4 feet, equal to the 

 distance of the 2 poles: about 10 feet from the window there was a silk line put 

 up across the room, by which that part of the line hung that had the ivory ball 

 on it. Below the cross line of the farthest pair of poles, was placed another 

 cross line, 4 feet from the ground ; to which was fastened the other end of the 

 communicating line, as mentioned in the experiment above. Then the leaf- 

 brass and tube being prepared as usual ; the tube being held over the line at 

 several distances, beginning towards that end where the ball hung, and so pro- 

 ceeding towards the farther end of the line, the leaf-brass was attracted pretty 

 strongly at the stations, not exceeding 2 or 300 feet ; but became still weaker 

 towards the farther end of the line : yet even at the end of it, the leaf-brass 

 would be lifted by the ball, when the tube touched the line, whose length was 

 886 feet. 



Coloured bodies, as Mr. Gray discovered in 1729, attract more or less, ac- 

 cording to what colours they are of, though the substance be the same, and of 

 equal weight and thickness : only that the red, orange, or yellow, attract at 

 least 3 or 4 times stronger than green, blue, or purple: but he lately found out 

 a new and more accurate method of making these experiments. 



