Hare’s Single Leaf Electrometer. 103 
proportionally great, but the deflagrating power was not 
increased in proportion. ‘The light was so intense, that 
falling upon some adjacent buildings, it had the appearance 
of sunshine. Having had another series of 300 pairs made 
for Dr. Macnevin of New-York, on trying it, 1 connected it 
with mine, both collaterally, and consecutively, so as to 
make in the one case a series of six hundred,—in the other 
a.series, half that in number, but equal in extent of sur- 
faces. The shock of the two, consecutively, was apparent- 
ly doubly as severe, as the shock produced by one; but 
the other phenomena seemed to me nearly equally bril- 
liant, in either way. | 
The white globules which you noticed, were formed copi- 
ously on the ignited plumbago, especially in vacuo. Ihave - 
not had leisure to test them, being arduously occupied, in 
my course of Lectures, and in some efforts to improve the 
means of experimental illustration. 
Account of an Electrometer, with a single leaf, by which the 
electricity excited by the touch of heterogeneous metals, is 
rendered obvious, after a single contact. 
Fig. 7. represents an Electrometer, with a single leaf sus- 
pended from a disk of zinc, six inches in diameter, which 
constitutes the top of the instrument. Opposite to this sin- 
gle leaf, isa ball, supported on a wire, which may be made 
to approach the leaf; or recede {rom it, by means ofa screw. 
Above the instrument, is seen a disk of copper, with a glass 
handle.* The electricity produced by the contact of cop- 
per and zinc, is rendered sensible in the following manner. 
Place the disk of copper on the disk of zinc, (which forms 
the canopy of the Electrometer:) take the micrometer 
screw in one hand, touch the copper disk with the other, 
and then lift this disk from the zinc. As soon as the sepa- 
ration is effected, the gold leaf will strike the ball usually, if 
the one be not more than ;2, of an inch, apart from the 
* For the experiment with this electrometer a metallic handle would an- 
awer. Its being of glass enabled me to compare the indication, thus obtain- 
ed, with that obtained by a condenser. 
