{ 324 ) 
Art. XII. — Description and Use of a very Sensible Elec- 
trometer^ for indicating the Kind of Electricity which is ap- 
plied to it. By Professor Bohnenberger 
i\.BOUT nine years ago, M. Behrens published the Description 
of an Electrometer, which indicates the kind of electricity that 
is presented to it“l* ; but it appears to have been forgotten, with 
the dry electrical columns, which formed an essential part of 
the apparatus. The Electrical Perpetual Motion of Zamboni 
reminded me of this electrometer,' and I engaged M. Butzen- 
geiger to execute one of them, which I shall proceed to de*- 
scribe. 
A cylindrical vessel of glass, about inches in diameter, 
and high, has fitted to it a brass-cap, from which two small 
dry electrical columns descend into the vessel, and are attached 
to the cap by screws, so that the one has its positive and the 
other its negative pole, making a slight projection above the 
cap. Each column is composed of 400 discs of gold and silver 
paper, glued together, and three lines in diameter, so as to fill 
two tubes of varnished glass. Each of these tubes is terminated 
below by a ring of brass, projecting a little, and rounded, which is 
in electrical communication with the discs. When the brass-cap 
is in its place, the columns descend vertically, and the lower ring 
is I th of an inch distant from the bottom of the glass. The axes 
of the columns are 1 inch and 7 lines distant, but may be 
brought nearer one another. From the centre of the cap rises 
a tube of glass, varnished within and without, and within the 
tube is a brass- wire kept in the axis by a cork, but touching the 
tube no where else. At the lower end of the brass- wire is sus- 
pended a piece of gold leaf 2| inches long and 3 lines wide, 
exactly in the middle of the interval betw^een the two columns, 
and parallel to their axis, if they are accurately vertical. At 
the upper end of the brass-wire is a small brass-ball, upon 
which may be screwed one of the. discs of a condenser, as in 
the electrometer of Volta. By this arrangement, the electrical 
* Translated from the Bibliotkeque Universelle, November 1820, p. 163=. 
f Annalen der Ph^sik, tom. xxiii. cap. 1. 
