On the Construction of De Luc’s Columns. 139 
upon a silk thread, and to transfer them to the tubes without derange- 
sent. 
The manganese which I employed with success, in the replenish- 
ment of the electric columns alluded to above, consisted mainly of 
needle shaped radiated crystals, aggregated intolumps. Mr. Lukens 
alleges that the crystallized manganese has always, agreeably to his ex- 
perience, proved the best for the construction of electric columns. 
The electrometer, with an electric column attached to it, as above 
represented, may serve to show the nature, as well as the extent of 
electric excitement; since, when an electrified mass is made to 
communicate with the brass ball A, from which the leaf is suspended, 
the latter ought to be attracted by that knob, which receives from the 
series an opposite excitement. Hence, the excitement of the elec- 
trified body being known, that of the poles may be detected ; or the 
latter being known, the excitement of the body may be discovered. 
This application of the electric series, is not, however, a new idea. 
lsaw many years ago a notice of an electrometer, associated with an 
electric column, in such manner, as to be used as an electrical dis- 
criminator. 
The great difficulty in resorting to this means of discrimination, is, 
that an electrified body may, by induction, produce in a conductor 
alternately, opposite states of electrical excitement. As it approxi- 
mates the conductor, it may cause it to receive, or give out electri- 
city ; of course, when retracted, the conductor will have the opposite 
excitement to that consequent to approximation. Supposing the 
brass ball of the electrometer in question, to be affected in the mode 
just described, the leaf suspended from it, must be successively at- 
tracted by each pole. Besides, the excitement may be so strong, as 
to render that of the series nugatory ; as in the case of a powerful 
magnet, which will attract either pole of a feeble one. 
The direction of the first pulsation of the leaf, is the best criteri- 
on; but reliance should not be accorded to one experiment, especi- 
ally when so easily repeated. I find that a gilt pith ball, if suspend- 
ed in place of the leaf, will vibrate for a time. It is, however, like 
the leaf liable to have its movements arrested by an adherence, to 
one or other of the knobs. 
