412 PHILOSOPHICAL TRANSACTIONS. [aNNO 1708. 



an attrition without. And for a further confirmation that the effluvia of glass 

 act only by a continuity of their parts, the following experiments may serve. 



ExPER. I. I took a piece of leaf brass, and laid it between two pieces of 

 wood, about an inch in thickness, and the same distance asunder. I then 

 applied a well rubbed tube to attract the "brass, as near as the wood would permit, 

 but gave it no manner of motion; then as soon as the wood was removed, and 

 the continuity of its sphere restored, the brass-leaf was driven to it very vigor- 

 ously, without any fresh attrition; which I think very plainly proves that the 

 action of the effluvia, at least in a great measure, is lost, if its parts are dis- 

 continued by any thing interposing or interrupting its spherical figure. Nay, 

 I have tried, by holding the tube in such a manner that its sphere might 

 meet with no interruption from the wood, in its circle round the axis of the 

 glass, yet neither would this exhibit any thing; by which I find, that if the 

 parts of the effluvia are in a manner interrupted, their action is destroyed, 

 or at least greatly impaired. 



ExpER II. Again, after the tube had been fresh rubbed, and the brass- 

 leaf scattered on the table, as usual; if a piece of paper were held to touch 

 the upper part of the tube, it would not attract at all, though approached 

 very near; but as soon as the paper was removed, it recovered its sphere of 

 activity, which was very sensible, by giving a brisk motion to those bodies, 

 which just before were at rest. And it was mentioned in the experiment 

 for producing light by the effluvia of the outer glass falling on the inner 

 exhausted glass in motion, that after the motions ceased, it was but approach- 

 ing one's hand near the surface of the outer glass to produce a light in the 

 inner one: whence, by these experiments it is plain, that the effluvia within 

 the glass were pushed more vigorously on the inner glass, by the approach of 

 the hand without, otherwise no light would have ensued. And further to 

 prove the stiffness of the body of the effluvia, it is observable, that when a 

 piece of brass-leaf is hunted about a room, that the brass swims or floats on 

 the surface of the effluvia; and as these are more or less exerted, so the brass 

 keeps its distance from them, nor will it by any means be suffered to sink 

 within their sphere, unless it meets with a body in its way, and then it is 

 attracted and returned again several times, with great swiftness. 



ExPER. III. Having tried the effect of discontinuing or interrupting the 

 effluvia of. the fricated tube on its outer surface, I was willing to try what 

 would ensue by filling its cavity with a body; which I did, by corking up one 

 end of it, and pouring in at the other dry writing sand, till it was nearly full: 

 the attrition was made, and when held towards the pieces of brass, as usual. 



