VOL. XXVI.j PHILOSOPHICAL TRAWSACTIOIfS. 411 • 



The Repetition of an Experiment on Motion given to Bodies included in a 

 Glass y by the Approach of a Finger near its outside : with other Experi- 

 ments on the Effluvia of Glass. By Mr. Fr. Hauhsbeey F. R. 5. N° 315, 

 p. 82. 



This experiment having been but imperfectly made before, I thought a repe- 

 tition of it would not be unacceptable to the society, since not only the 

 apparatus was better adapted, but the appearance was much more conspicuous. 

 For it was observable, that after the motion and attrition had been continued 

 about 2 or 3 minutes, and then ceasing, the threads within seemed to hang in 

 a confused position, and were not instantaneously erected, but in about 3 or 4 

 seconds of time they were so, every way towards the circumference of the glass ; 

 and seemingly with so much eagerness, that a motion of the glass alone would 

 o-ive them no great disorder: but the most surprising thing, was to see a motion 

 given them by the approach of one's hand, finger, or any other body, at more 

 than 3 inches distance from the outer surface of the glass, although the threads 

 within did not touch the inner one. And it was further observable, that every 

 repetition of the motion of the wheel, and a new attrition of the glass, the 

 distance at which the threads might be moved, seemed to be increased. And 

 I have since found that the threads could have a notable motion given them 

 by blowing towards the glass with one's mouth, at 3 or 4 feet distance ; by 

 which means the air was put in motion, and consequently the effluvia of glass 

 were so too. At another time, suddenly clapping my spread hands on the upper 

 and lower parts of the globe, there was such a violent agitation of the threads 

 within, as was very surprising, and which continued for some time. 



In the experiment where the directed threads on the outside of the glass 

 would fly the approach of any thing held near them, it seems to me that the 

 parts of the effluvia are stiff, and continued ; so that when any part of them 

 are pushed, all that are in the same line suffer the same disorder. So likewise 

 in the above experiment, allowing a continuity of parts, the effluvia within, 

 and those without, are all of a piece or continued, (for they are both produced 

 by the same attrition) so that when the effluvia are pushed or disturbed without, 

 the effluvia within, in the same direction, are so too, and consequently the 

 threads which are upheld and directed by them. The effluvia arising from the 

 glass, seem to be nothing else but part of the same body emitted from it by 

 rubbing ; and therefore I think can be no impediment to the motion of its own 

 effluvia, for otherwise I do not see how the effluvia within can be produced by 



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