New Outlines of Chemical Philosophy. 285 
ecard, about an inch square, between the two bobs of the pen- 
dulums*. A piece of card paper, rather less than an inch square, 
is inserted into the place where the card was cut out, and be- 
tween the two ends of the wires, for the electric spark to pass 
through. As soon as this card has, been perforated, it is taken 
out, and another piece of equal dimensions put into its place ; 
and thus a number of experiments may be made with very little 
trouble. 
The second improvement consists in fixing a thread to each 
pendulum rod. These threads pass through two separate holes 
in the card in contrary directions, so that by taking hold of their 
ends the pendulums may be drawn close to the plane of the in- 
strument. 
When an electric charge is passed through the two wires, the 
pendulums are thrown off in contrary directions, and conse- 
quently the threads are drawn through the card, and show the 
mechanical forces of the two elements. 
The length of the thread drawn through the card in eleven 
experiments by the positive force, thermogen, was 23 inches 5 
and the thread drawn through the card, at the same time, by the 
other force, improperly called negative electricity, measured 22 
inches. 
In four of these experiments the mechanical forces were equal: 
in some of the rest the positive, or thermogen, acted with greater 
energy than the photogen; in others it acted with less: but these 
differences were only such as might have been expected from the 
nature of the elements which were the objects of investigation. 
Whence we may infer, notwithstanding this small difference, 
that the electric spark is composed of two elements passing 
through each other with equal forces, in contrary directions. 
Consequently, positive and negative are words that have no de- 
finite meanings in chemical philosophy; thermogen and photo- 
gen are more appropriate; and as I have clearly defined those 
terms, my meaning cannot be misunderstood by men of science. 
a 
Lynn, April 18, 1814. E, WaLKER. 
To Masers. Nicholson and Tilloch. 
* See vol. xlii. Plate IIT. fig. 3, 
XI. Description 
