Qg ELECTRICAL EXPERIMENTS ON GLASS. 



»eter, gilt or silvered all over, with its edges well rounded 

 off, and supported by a glass foot at such a height, that 

 the balls of the two curved tubes may rest on a little me- 

 tallic circle of three or four inches diameter cemented to the 

 centre of the upper side of the glass. Below I place a 

 knobbed exciter against the edge of the gilt top of the in- 

 sulating stand, leaving about a line distance between them, 

 as in the preceding experiment. In this state I begin to 

 charge. At the tirst turns of the plate it frequently hap- 

 pens, that we see round the little upper coating some flashes 

 gf electric light; but if the glass be thin, they will soon 

 disappear, and though you continue to turn the plate a 

 thousand and a thousand times, the square will be charged 

 to the whole capacity of the coated glass, but will afterward 

 P&s^e of the yield a continual passage to the fluid. By this experiment 

 fluid through ' ln t| ie dark I have been convinced of the reality of the pas- 

 glass, sage of the fluid through the pores of glass as through a 

 filter of capillary tubes. This experiment was repeated 

 several times in the presence of the friend, who suggested 

 to me the idea of the oxidation of the metallic coatings, 

 comparing them with those, which probably take place in 

 the great in marble quarries. He is inclined to consider 

 this as an experbnentum crucis with respect to this passage 

 F.lectricity de- of the fluid. It is thus he is equally convinced, that the 

 Dy oxiding S electric fluid oxides the most tenacious metals partially in 

 thera. its passage, before it destroys them at the instant of the de- 

 velopement of the gasses, which takes place in my metallic 

 cylinders. He is an excellent pneumatic chemist, and fre- 

 quently repeats to me, that caloric penetrates all bodies, 

 that all consequently have pores, and that the penetration 

 of the electric matter through those of glass is in no way 

 inconsistent with the true principles; but that the pre- 

 tended removal of it from one side of the glass, which re- 

 ceives a superabundance of it on the other, is contrary to 

 the axiom of his master, Lavoisier : there is no motion, no 

 sensation, unless the impulse acts through the thickness : 

 and hence, if we grimt this expulsive action, we must admit 

 a capacity of penetration in the fluid. 

 Common glass . In his presence I repeated the experiment with common 



ladedbJt i>er * S lass ' This ) rields a P assa o e t0 the fluid with !ess ease, but 



on 



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