AERIAL COLUMN AND AERIAL ELECTROSCOPE. gjf 



known the same paper of which I ara speaking, he would have in the galvanic 

 seen, in p. Ql, that I have made the very same experiments di- P 

 rectly on the galvanic pile ; and that I found the same grada- 

 tion of plus and of minus, from the middle point, as in the 

 column. Only these operations cannot be so long continued on 

 the pile, because its electrical signs are diminishing in propor- 

 tion to the erosion of the surface of the metals. But Dr. May- 

 cock could not be informed of these electrical phaenomena of 

 the galvardc pile ; because, as it appears, he has not used it| 

 and his galvanic observations have been only on the galvanic ^ . , . 

 apparatus of troughs, which, as I shall show in a future paperj differently, 

 has deceived him. 



10. I now come to another class of experiments, which, it Q^l^^Y proofs 

 seems, are also unknown to Dr. Maycock ; for, had he read of the circula- 



them, he would have found evident proofs of a irculation of the *'"" ?^ *'*^^ 



electric fliucl 

 electric fluid, when the extremities of the column, or of the in the pile. 



pile, are connected together. These experiments consist in pro- 

 ducing the connexion of the extremities by different bodies, and 

 observing their effects on th^ gold leaf electroscopes. It has 

 been seen, in the above experiments, that, when the extremities 

 of the column are unconnected, there is an accumulation of the 

 electric fluid at the extremity A, where the gold leaves diverge 

 as positive, and a deficiency at the extremity B, where they di- 

 verge negatively. If a good conductor be applied to produce 

 the communication between the extremities, the gold leaves 

 fall on both sides : if it be a perfect nonconductor, their diver" 

 gence is not altered : but if an imperfect conductor be applied, 

 they fall, in proportion to the conducting faculty of the body. 



1 1 , These experiments begin at p. 91 of the same number Glass requires 



of your Journal. I made them for the purpose of ascertaining varnish for a 

 . , . . , . . , r , , . , . perfect iastt- 



a very essential point m electncity, that of the best msuiation i^^^q^^^ 



o( a\\ o\ic electrical apparatuses ; having found, that the want 



of a complete insulation may lead to errour. Glass is the only 



body used, on account of its solidity, for pillars in all these • 



apparatuses 3 and it has, in this respect, the essential property 



not to he permealle to the electricuid : but, it is not a perfect 



nonconductor 5 the electric fluid moves, though slowly, along 



its surface, and to prevent it, it is necessary to cover it with 



some insulating varnish. These experiments, therefore, I 



made first, in order to find out which were the lest conductors j 



next. 



