162 On Electritity. 
from the inside of the jar passed from p to n, because art 
indent was made downwards at the point e; and it is also 
evident, that the power from the outside of the jar passed 
in the direction from x to #, as an indent was made up- 
wards at the point hk. Hence we may fairly conclude, that 
the electric spark consists not of one power only, but of 
two distinct positive powers acting in contrary directions 
and towarde each other. 
Experiment 2. I placed a single card upon a table, 
with a piece of wire upon it and another piece under it, so 
that their ends were one above the other; then two other 
cards were taken, and a piece of tin-foil placed upon the 
centre of each. One of these cards was placed under the 
bottom wire, with the tin-foil upwards, and thé other was 
placed upon the top wire, the tin-foil being downwards. 
An electric charge being passed through the two wires 
produced the same phenomena as those before mentioned; 
the middle card was perforated, the tin-foil upon the ander 
card was indented downwards, but that upon the upper was 
indented upwards. . 
I communicated these experiments to Mr. Murray, phi- 
losophical lecturer, requesting him to repeat them, and the 
following is extracted from his answer, dated Swaffham, 
17th July, .1813: 
* 1 took a single card,” says Mr. Murray, ‘‘ and placed 
one wire above it and another below, with the ends one 
above the other,” &c. and proceeded as you direct: the 
result proved your conclusion to be correct, for the tin- 
_ foil. both above and below the perforation was indented and 
in contrary directions. 
“‘The theory of two powers moving contratiwise re- 
ceives validity from the following experiment. The cards 
and tin-foil slips being used as before, I placed two points 
below instead of one, with one above; two corresponding 
indents were made on the tin-foil wpwards and ouly one 
downwards. I reversed the experiment, and the two points 
being above the card, there appeared two indents down- 
wards and only one upwards. 
_ **T repeated these with uniform pbenomena and un- 
varying results, 
You will think, I doubt not, with me, that the last 
mode of conducting the experiment places the subject in a 
point of view, beyond a doubt of the conclusion we have 
mutually drawn. ; 
; _ * Lam, dear sir, with great respect, &c. 
a de «J, Murray.” 
By 
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