414 PHILOSOPHICAL TRANSACTIONS. [atSTNO 1708. 



experiment of the above-mentioned glass, but could obtain no such appearance 

 without touching it. This in a great measure shows the weakness of its efflu- 

 via. I likewise tried what light might be produced from it, by giving it motion 

 in vacuo; and though I was forced to use flannel there, yet a very distinguish- 

 ing light appeared on each arm of the brass spring, that gently embraced it; 

 and I doubt not but if my hand could be made use of to rub the wax in such a 

 medium, the light would have been much greater; for the light produced by 

 the attrition of the flannel on the wax in vacuo, was rathar better than that 

 which was produced by the attrition with my naked hand in open air. From all 

 which experiments it appears, that the largeness or smallness of light or at- 

 traction, producible from bodies by attrition, proceeds from the number and 

 strength of their respective effluvia. 



Further, I caused two wooden cylinders to be turned, of the same dimensions 

 as mentioned in the experiment of the sealing-wax ; and in the same manner as 

 in that, I coated their outer surfaces, one with melted sulphur, the other with 

 colophony or rosin, mixed with brick-dust, (put into it to bind and make it the 

 more hard); and first I fixed the cylinder, which was clothed with the melted 

 flour of sulphur, to give it motion as usual; and after my hand had been 

 held on it a little while, I caused the motion to stop, then bringing near it the 

 ring with threads, mentioned in former experiments, the threads were attracted 

 and directed to its centre, but not so strongly as to the sealing-wax. And on 

 several trials this was much the same. I then tried the rosin in the same man- 

 ner, and found its electrical quality much stronger than the former: for the 

 threads were driven towards its centre, seemingly with greater vigour, than to- 

 wards that of the sealing-wax; but the rosin at that time was not quite cold. 

 In both these experiments, the threads would fly the approach of the finger; 

 but if sealing-wax or amber were held near them, they would very eagerly fly 

 and adhere to them, without being rubbed; and this I never took notice of be- 

 fore. I further observed, that the rosin, while warm, would attract brass-leaf 

 at an inch or two distance without any attrition. But next day when I came to 

 repeat the experiment, its electricity was very inconsiderable, as well as that of 

 the sulphur. At night 1 tried what light these bodies would yield on their at- 

 trition in the dark; but could produce none from the rosin, and indeed but very, 

 little from the sulphur, and that not by my hand, but by holding the ends of 

 my nails very hard on it while it was in motion. I tried likewise whether the 

 sulphur would emit any light by its attrition in the dark in vacuo; but could 

 discover none. 



The most surprising of all experiments that I have met with yet, are the fol- 

 lowing. I took my glass globe, that I use for showing the experiment of the 



