OI? THE ELECTRIC COLUMN. ^5 



the glass; therefore these differences may become a parti- 

 cular object of experiments, concerning- the property of 

 different glasses for electric purposes, by comparing the ef- 

 fects of different rods on the electroscopes of the column ; 

 much care being taken, that all effect of friction be dissi- 

 pated. \^'ith respect to varnishes, a proper sealing wax 

 laid over the glass when hot is the best coating which I have 

 found ; a rod of this kind produces no change in the elec- 

 troscopes. But all sealing waxes have not the same pro- Sealing wax 

 perty, and before I had devised this mode of trial, I was j^j^j, ^* '*'^' 

 sometimes disappointed in the construction of the small set 

 of electric apparatusses, which 1 have mentioned in the 

 former paper, even in that of the electroscopes of the co- 

 iamn, as the top of tlieir glass bottle must be insulating. 

 The sealing wax reckoned the finest, because it melts more but not the 

 easily and spreads more smoothly, is not fit for this purpose, 

 its softness being produced by spirit of wine. In general, 

 for this essential choice of an insulating coating on glass, 

 the column is very useful ; for by laying the different cout- 

 ittgs on glass rods, and placing these on the hooks of the 

 co/Mwn, those which will be found to diminish the divergence 

 in the electroscopes are not completely insulating, and that 

 coating must be used, by which the divergences are not af- 

 fected. 



1 come to the impression produced on the column itself. Effects of fric- 

 when there reipains some efi'ect of friction on the insulating ^io" o" 'he ia. 

 rods applied to it. The experiments on this object will, at 

 the same time, afford a new veriflcation of the cause which 

 I have assigned to the motion of the electric fluid in the co- 

 lumn (or the pile), by what is called the electric influence', 

 the laws of which, tirst really determined by Sig. Volta, I 

 have explained by some modifications of tlie vector, which 

 will be perceived in the following experiments; showing at 

 the same time the effect of the ambient air, such as I have 

 determined it. The proper time for these experiments is 

 also when, from the electric state of the ambient air, there 

 is not much divergence in the electroscopes of the column. 

 They may be made with naked glass, which /ric/f on ren- 

 ders positive; and with a glass rod covered with sealing wax, 

 which thus becomes negative. 1 shall explain the pheno- 

 mena 



