533 
Electricity by Contact. 
3. It appeared to me very improbable, that those pulverulent 
bodies should turn out so very different in their electrical rela- 
tion towards the metals, considering that the opposition between 
acids arid bases is riot an absolute, but only a correlative one, 
and that it might be impossible to anticipate the relation of silica , 
for instoce, and of those bodies in general, which are possessed 
neither of a marked acid, nor of a basic nature. 
When I touched magnesia with a plate of zinc, the diameter 
of which was ~7^ Par. inch, with due regard to the precautions 
necessary in those experiments according to Sir H. Davy, the 
Zinc was found positively, the Magnesia negatively electrified. 
In this experiment I had employed the electrometer of Volta, 
with its condenser. By this contrary result, I was induced to 
repeat the greatest part of Sir H. Davy’s experiments. 
In order to avoid repetitions, I shall premise all that is com- 
mon to the following experiments. 
I employed always the new electrometer, with the two Zam- 
bonic piles, described by Professor Bohnenberger, in the 
‘‘ Tubinger Blatter,” which is very nicely executed by M, Bu- 
ZENGEiGER of Tubingen %. 
From the superior sensibility of this instrument, the use of 
the condenser was superseded, and the species of electricity was 
immediately indicated. 
The substances were heated in a covered platina crucible, and 
ignited, when their nature allowed it. The crucible, when still 
hot, was put on a bath of dry mercury, and covered with a per- 
fectly dry glass, Thus, the substance in the crucible assumed 
the temperature of the surrounding atmosphere, without having 
been in contact with the air. Twenty-four hours passed ; it was 
touched, still confined in the crucible, with round plates of zinc 
or copper, of a diameter 2 Par. inches, insulated by a glass 
handle. 
No difference was perceived, whether the substance was insu- 
lated or not. 
The experiments were always, if the contrary is not expressly 
noticed, insulated in a dry and fine season, and the temperature 
varied from -{-12° to -j-16° of Reaumur. But as I have found 
no difference m this respect, provided the substances had been 
* This curious Electrometer is described in vol. iv. p. 324. of this Journal, 
VOL. Vl. NO. 11. JANUARY 1822. C 
