an Electric Column composed of Discs of Zinc and Silver. 243 
the electrometer, the leaves opened instantly nearly to their full 
extent; and though the finger was put upon the tube in various 
places, the leaves struck, and continued to strike, the sides of the 
electrometer. 
For a considerable time, during which a great number of ex- 
periments similar to the above were made, the results obtained 
were uniformly the same as the preceding, except in two or three 
instances which occurred when the column was insulated, and 
the leaves of the electrometer had only a small divergence: in 
those instances the leaves seemed to éverease rather than diminish 
their divergence when the glass tube was touched; especially 
when the finger was laid upon it near its negative extremity: but 
the difference of divergence being exceedingly small, I was at 
first inclined to think that my sight had deceived me. I deter- 
mined, however, should the apparent anomaly recur in any future 
experiment, to ascertain whether it were real or fantastical ; but 
some weeks elapsed before I had the opportunity of decisively 
establishing its reality. The subsequent experiments made on 
the 18th of the present month exhibit this remarkable fact di- 
stinctly, and show that opposite effects may sometimes be pro- 
duced by the same cause. 
The column had been in the position as in Series 2, for several 
hours ; the leaves of the electrometer diverged about +'.th of an 
inch. The glass tube was touched near its middle with the 
finger ; the divergence of the leaves was not lessened as is ge- 
nerally the case, but, on the contrary, seemed to be increased by 
it; the finger was therefore again placed upon the tube, and the 
contact continued ; it then became evident that the leaves were 
opening wider, and in about two seconds their original divergence 
was fully doubled ; the finger: was removed from the tube, but 
the leaves still retained their divergence. As no alteration took 
place in the leaves, the finger was next laid upon the waxed ex- 
tremity of the tube next to the electrometer; the leaves then 
very slowly lest their divergence, and finally closed. As soon as 
their separation was again perceptible, a finger was laid upon the 
glass tube near to its negative extremity; the leaves now opened 
more quickly than before, and presently attained a divergence of 
one-fourth of an inch. The finger was withdrawn from the 
tube, and after a few seconds was again laid upon the waxed ex- 
tremity next the electrometer; the leaves gradually diminished 
their divergence ; hut before they quite closed, the finger was 
laid upon the opposite (negative) waxed extremity; the leaves 
began to open wider, and as the contact was continued, they 
soon regained their former divergence of one-fourth of an inch. 
When the negative end of the column was made to communi- 
cate with the ground, the leaves attained a divergence of only 
Q 2 five- 
