On the Construction of De Luc's Columns. 1 39 



upon a silk thread, and to transfer them to the tubes without derange- 

 ment. 



The manganese which 1 employed with success, in the replenish- 

 ment of the electric columns alluded to above, consisted mainly of 

 needle shaped radiated crystals, aggregated into lumps. 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 |)rass 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. 

 1 saw 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. 



