346 PHILOSOPHICAL TRANSACTIONS. [aNNO I7O7. 



may be subject to, I cannot determine. I have tried the same experiment with 

 a glass exhausted of its air, but it afforded nothing observable. 



ExPER. III. Being a Repetition and Improvement of the former. — I procured 

 a glass of a more suitable form, for a repetition of the foregoing experiment, 

 being nearly a hemisphere, with a neck to it, by which it was screwed to one 

 end of a spindle, and had motion given it by the large wheel as usual. This 

 manner of fixing, and the figure of the glass, gave me the liberty of rubbing 

 it as well within as without ; though on trial I find, that either way is much 

 the same ; for when the threads are held within, and the attrition made on the 

 outside, or the contrary, or the friction made on the same side the threads are 

 used, it makes very little difference. To proceed : when the threads were fixed 

 on an axis within, and the motion and attrition made as usual, the threads then 

 pointed to the axis ; and then, if a finger was approached near the outside of 

 the glass, a motion would be given to the point of the thread that was nearest 

 it within ; and at the same time, if the threads were removed to the outside, 

 and the finger held within, the like motion uould be given to them there. 

 Generally, the threads seem to fly the approach of the finger ; yet sometimes 

 I have seen them jump suddenly towards it, at more than an inch distance. It 

 is remarkable, that the figures represented by the directed threads, from, and 

 towards the centre, not only mimic, but seen very much to resemble the cen- 

 tripetal and centrifugal tendencies of bodies in their motions either way. 



ExPER. IV. Showing that the Effluvia of Glass are capable of performing 

 the Office of Attrition ; causing a Lights by falling on an exhausted Glass in 

 Motion, as if rubbed by the Hand. — That the effluvia of glass are very con- 

 siderable in the productions of divers phaenomena, has already been abundantly 

 proved ; but that they should act the part of a solid body, by performing the 

 office of one, is still more extraordinary : and that they do so, the following 

 experiment sufficiently demonstrates, and seems to corroborate a hint I gave in 

 the 2d experiment of their emulating such a body, by causing a thread to fly 

 the approaching finger. I took a large globe glass, about Q inches diameter, 

 which having exhausted of its air, I fixed to give it motion, by the machine 

 described in Philos. Transact. N° 304, its axis standing perpendicular. An- 

 other globe glass, about the size of the former, was placed to give motion to it 

 by a new machine, and was wrought with its axis parallel to the horizon. This 

 last globe, with its contents of common air, was fixed so as to move within an 

 inch of touching the others. In these positions the machines were worked, 

 and the naked hand applied to the unexhausted glass, the effluvia of which in 

 a little time reaching the exhausted glass in motion, immediately produced a 

 light on that part of it nearest to the other, without the assistance of a touch 



