VOL. XXVI.] PHILOSOPHICAL TRANSACTIONS. 415 



included threads, which would point every way from the centre to the circum- 

 ference on its attrition; and in that state a motion might be given to those 

 threads, by the approach of one's hand near its outside. But this proceeded 

 from the effluvia of its own body exerted by rubbing, therefore not so much to 

 be wondered at. But that those threads contained in the same globe, should 

 have motion given them by the effluvia of a heterogeneous body separate from 

 it, and the globe at the same time to have no manner of motion or attrition 

 given it, is very surprising; and that it is so, is matter of fact ; for when I 

 held rubbed sealing-wax near the outside of the globe, the threads within 

 would have motion given them in a very odd manner, though the body of wax 

 touched not the glass by 3 or 4 inches. The like I found might be performed 

 by a rubbed glass tube, or by amber ; and if the threads were placed in a bottle 

 well corked up, or any other close glass, I suppose it would answer the same. 



I have since repeated this experiment with brass leaf, covered with a glass 

 dish on a table; and it was observable, that though the dish was very thick, on 

 holding the well rubbed sealing-wax over it, the pieces of brass-leaf within 

 would have a brisk motion given them, and continue so for a considerable time, 

 ere the wax would require any fresh attrition. But this appearance will not 

 always succeed ; for some time after, attempting the same experiment, I could 

 by no means make it answer as before; the temperature of the air being then 

 altered, its moist effluvia were condensed on the glass ; and so long as it re- 

 mained under such circumstance, it was attempting it in vain. But I found if 

 the glass was a little warmed by the fire, or placed a while in the sunshine, or 

 well rubbed with a warm dry linen cloth, any of which, whereby the humid 

 effluvia might be evaporated, that then the included pieces of brass leaf would 

 have as brisk a motion given them, from the fricated wax as before. Now, that 

 the fire, sunshine, or the rubbing the glass with a warm dry linen cloth, nor 

 only clears it from the moist effluvia condensed on it, but likewise gives motion 

 to the particles of the glass itself, which motion seems to produce effluvia, which 

 in conjunction with that of the sealing-wax, facilitates its action on the said 

 bodies, I conclude from this particular, viz. that when I had warmed the glass 

 by the fire, or had evaporated the humid effluvia by any of the other means, I 

 found I could give motion to the included brass-leaf, by only rubbing my finger 

 on the outside of the glass, without the assistance of the wax. But when the 

 well rubbed wax was held over it, the motion of those bodies would be much 

 increased; and it was observable, that sometimes the brass-leaf would continue 

 to be in motion after the wax was withdrawn from it. But when the air is 

 naturally warm, and free from humid vapours, there need none of the above- 

 mentioned means to assist the effluvia of the wax to give motion to the in- 



