18 
IS THE SUPPLY OF ELECTRICITY DUE TO METALLIC 
is, that as it is impossible to produce such ab- 
sence of matter by artificial means, it seems 
unnecessary to dwell upon it. 
The experiments of Harris go to prove that 
electrical divergence completely independent 
of atmospheric attraction, and is therefore in 
accordance with the opinion w'ith which he 
sets out, that electricity is a subtle material 
agent, essentially involved in the constitution 
of ordinary matter. 'I’he experiments, how- 
ever, upon which such deductions can be 
founded, it is obvious, must be conducted with 
the greatest delicacy, and in such cases, ab- 
solute certainty is scarcely to be looked for. 
EXPERLMENTAL RESEARCHES 
IN 
ELECTRICITY. 
Sth, Series* 
By M. Fauadav. 
The paper of Dr. Faraday constitutes the 
Eighth Series of his researches in electricity, 
and consists of corrected and extended views 
of the theory contained in his Fifth and Se- 
venth Series. The whole paper is pregnant 
with important matter. It has been objected 
to Dr. Faraday’s papers on electricity that 
they are difficult to understand, in coiise- 
querice of the new nomenclature which he 
has introduced, and perhaps there is reason, 
in some instances, in similar complaints, for 
surely, it is said, when plain English words 
can express facts or opinions, it is improper 
to substitute technical expressions, either in 
science or literature ; and a language which 
can muster, in alphabetical array, seventy- 
five thousand words, does not stand in need 
of unnecessary innovations. Such observa- 
tions, however, do not apply in the present 
instance : because, the new terms are few, 
and obviate much circumlocution. They may, 
however, be attended to with propriety by 
those who are only entering upon discovery. 
In medicine, more especially, it is too obvi- 
ous that technicalities have served, in many 
instances, to form cloaks for ignorance and 
quackery. 
In the present series, the author enters upon 
the investigation of the important point whe- 
ther the supply of electricity is due to metal- 
lie contact or chemical action. For the pur- 
pose of determining this point, he took a 
plate of zinc, about eight inches long and hal f 
an inch wide, which was cleaned and bent in 
the middle to a right angle, A plate of plati- 
num, about three inches long and half an inch 
wide, was fastended to a platinum wire, and 
the latter bent to a right angle. These two 
pieces of metal were arranged together, but 
outside a vessel, and its contents, which con- 
sisted of dilute sulphuric acid, mingled with 
a little nitric acid. A piece of folded bibu- 
lous paper, moistened in a solution of iodide 
of potassium, was placed on the zinc, and 
was pressed upon by the ends of the platinum 
wire. When under these circumstances, the 
plates were dipped into the acid of the vessel 
described, there was an immediate effect at 
the bibulous paper, the iodide being decom- 
posed, and iodide appearing at the anode, 
i. e., against the end of the platinum wire. 
As long as the lower ends of the plates re - 
rnained in the acid, the electric current con- 
tinued, and the decomposition of the iodide 
proceeded. On the removing the end of the 
wire from place to place on the paper, the 
effect was evidently very powerful, and on 
placing a piece of turmeric paper between 
the white paper and zinc, both papers being 
moistened with the solution of iodide of 
potassium, alkali was evolved at the cathode, 
against the zinc, in proportion to the evolu- 
tion of iodide at the anode. Hence the de- 
composition was perfectly polar, and de- 
cidedly dependent upon a current of electrici- 
ty passing from the zinc through the acid 
to the platinum in the vessel, and back 
from the platinum, through the solution to 
the zinc at the bibulous paper. The fact 
of the decomposition being produced by 
the electrical current, was proved by the 
circumstance of the decomposition ceasing 
when the acid and its vessel were removed 
from the plates, and being again removed 
wheri the contact was repeated. The same 
position was deduced by varying the experi- 
ment, amalgamating pieces of zinc over the 
vyhole surface, and employing dilute sulphu- 
ric acid in the vessel. The same effects re- 
sulted when caustic potash was used instead 
of acid, and also when brine was substituted. 
The inferences which the author draws are, 
1st, That metallic contact is not necessary 
for the production of the voltaic current ; 
2d. That a most extraordinary mutual re- 
lation of chemical affinities of the fluid exists 
which excites the current and the fluid which 
is decomposed by it. 
The use of metallic contact in a single pair 
of plates appears evident from the experi- 
ments, For when an amalgamated zinc plate 
is dipped into dilute sulphuric acid, the force 
of chemical affinity exerted between the me- 
tal and the fluid is not sufficiently powerful 
to cause sensible action at the surfaces of 
contact, and occasion the decomposition of 
water by the oxidation of the metal, although 
it is sufficient to produce such a condition of 
the electricity as would produce a current if 
there was a path open for it. 
Now, the presence of a piece of platinum 
touching both the zinc and the fluid to be 
decomposed opens the path required for the 
electricity, because only one set of opposing 
affinities are to be overcome ; whereas, when 
metallic contact is not allowed, two sets of 
opposing affinities must be conquered. Some 
have considered it impossible to decompose 
bodies by Hare’s calorimeter, or Wollaston’s 
powerful single pair of plates, but this was 
owing to their considering the decomposition 
of water a test of the passage of an electric 
current. But the author observed that bo- 
dies would differ in facility of decomposition 
by a given electric current, according to the 
condition and intensity of their ordinary che- 
mical affinities, and he has corroborated the 
fact by new experiments. In employing dif- 
ferent fluids to excite the action, he procured 
currents of electricity varying in intensity 
and by consequence in their defects. Dilute 
sulphuric acid acting upon the zinc and plati- 
