KLEdtRICAL EXPEfctMENtS ON GLASSo Q$ 



the metal of the c*p acts no longer in competition with the 

 glass to fix it in the metal of the inferior coating, I raised 

 the cap three Or four inches, and held it thus a few seconds 

 without seeing the least spark pass between the inferior 

 Coating- and the knob of the exciter ; but the moment I drew 

 electricity from the cap, a strong spark was emitted toward 

 the ground. This fact gave me the more pleasure, as it 

 still more confirmed the theory of elective attraction, on 

 which all my deductions are founded. I know not whether 

 this experiment be new, but I do not find it in Libes, Haiiy, 

 or the French translation of Fischer, which has lately ap- 

 peared with notes by Biot ; and it appears to me to merit 

 attention, as it throws light on the theory of thunderstorms. Thunder- 

 Here the column of air interposed between the cap and the 

 glass prolongs the retaining power of the glass to six, eight, 

 or even fifteen or sixteen inches in dry weather : there I 

 figure to myself a large plate of air between those clouds 

 that traverse the atmosphere in opposite directions, the elec- 

 tric fluid of which remains insulated till the moment when 

 the elective attraction surpasses the retaining action of the , 

 stratum of air, &c. This experiment also shows the reason Doubles. 

 why the new doubler Of electricity, invented a few years 

 ago in England, charges its plate&on approaching and se- 

 parating them repeatedly, and acquires through the stratum 

 of air that separates them so intense a change* that the plates 

 discharge themselves spontaneously *. 



The glass electrophorus, mentioned by Mr. Lugt as well Glass electro* 

 as Sigaud de la Fond, but the effects of which, as it appears p 10rUS ' 

 to me, have not been compared with those of the Leyden 

 phial, has lately engaged my attention. The following are 

 the experiments I have been led to make, and in my mind 

 they render still more probable the complete saturation of 

 the Leyden phial by the retaining affinity of the substance 

 of the glass itself. 



I take a square of German sheet glass [verre blanc de Experiment. 

 Boheme] twenty or two and twenty inches wide, and 

 place it on an insulating stand seven or eight inches in diu- 



* See Journal, vol. IX, p. 19. It is for September, 1804, not 1805, 

 as misquoted by the writer in the Journ. de Thysique. 



-Vol. XXIII— May, 1809. F meter, 



