Mr. Davy’s Lecture on some 
a measure may be found of the artificial energies, as to inten- 
sity and quantity produced in the common electrical machine, 
or the Voltaic apparatus, capable of destroying this equili- 
brium ; and such a measure would enable us to make a scale 
of electrical powers corresponding to degrees of affinity. 
In the circuit of the Voltaic apparatus, completed by 
metallic wires and water, the strength of the opposite electri- 
cities diminish from the points of contact of the wires towards 
the middle point in the water, which is necessarily neutral. 
In a body of water of considerable length it probably would 
not be difficult to assign the places in which the different 
neutral compounds yielded to, or resisted, decomposition. 
Sulphate of barytes, in all cases that I tried, required immediate 
contact with the wire : solution of sulphate of potash exhibited 
no marks of decomposition with the power of 150, when con- 
connected in a circuit of water ten inches in length, at four 
inches from the positive point ; but when placed within two 
inches, its alkali was slowly repelled and its acid attracted. * 
Whenever bodies brought by artificial means into a high 
state of opposite electricities are made to restore thejequili- 
brium, heat and light are the common consequences. It is 
* In this experiment, the water was contained in a circular glass bason two inches 
deep, the communication was made by pieces of amianthus of about the eighth of 
an inch in breadth. The saline solution filled a half ounce measure, and the distance 
between the solution and the water, at both points of communication, was a quarter 
of an inch. I mention these circumstances because the quantity of fluid and the 
extent of surface materially influence the result in trials of this kind. Water included 
in glass siphons forms a much less perfect conducting chain than when diffused upon 
the surface of fibrous nonconducting substances of much smaller volume than the 
diameter of the siphons. I attempted to employ siphons in some of my first experi- 
ments ; but the very great inferiority of effect as compared with that of amianthus 
made me altogether relinquish the use of them. 
