280 
DR. RITCHIE’S EXPERIMENTAL RESEARCHES 
It is easy to neutralize the effects of these experiments by one much more strik- 
ing, in which decided voltaic effects are produced by one metal and one liquid. 
The best mode of proving this is by the following experiment : 
Exp. I. — Form a galvanometer with a coil of copper wire, and leave the ends 
projecting about two feet. Roll one of the ends about a small rod so as to 
form a close spiral about a quarter of an inch in diameter. Roll the other end 
of the wire about a large rod or glass tube so as to form another spiral of half 
an inch in diameter. Place the small spiral within the larger one, and im- 
merse them in water containing a quantity of nitric acid, and a very consi- 
derable electro-magnetic effect will be produced. 
I have given this experiment to prove, in a manner free from every objection, 
that voltaic action may be produced without the contact of dissimilar metals, 
and consequently without the aid of that mysterious force, termed by Volta 
and his followers electro-motive. 
2. Those who adopt the theory of Volta have taken it for granted, without 
a shadow of proof, that the free positive electricity which they conceived they 
had detected on the surface of the zinc, was that which circulated through the 
liquid and metallic conductors, and produced all the phenomena of voltaic 
electricity. M. Parrot of St. Petersburgh has examined the fundamental ex- 
periments of Volta with the most scrupulous regard to accuracy, and observed 
that sometimes a minute portion of free positive electricity was detected on 
the zinc and at other times on the copper. This minute portion was obviously 
developed by friction or simple pressure of the zinc and copper plates ; for 
when the plates were soldered together, and the experiment repeated, as de- 
scribed by Volta, he could not detect the slightest sign of free electricity *. 
From the marked difference between the effects of free and voltaic electricity, 
it is extremely improbable that a minute portion of common electricity could 
ever acquire the characters of voltaic. Common electricity is diffused over the 
surface of the metal; — voltaic electricity exists within the metal. Free elec- 
tricity is conducted over the surface of the thinnest gold-leaf, as effectually as 
over a mass of metal having the same surface; — voltaic electricity requires 
thickness of metal for its conduction. 
3. A powerful argument against the theory of free electricity becoming com- 
* Annales de Chimie, xlvi. 363. 
