BEFORE COMPLETION OF THE VOLTAIC CIRCUIT. 
191 
pile being attached to the outer, and one from the other to the inner coating. On 
the two small balls which are fixed to this really beautiful and simple instrument 
being approximated to about ^th of an inch, the jar was charged and discharged 
every three seconds, and this action continued for several minutes without the 
slightest variation. 
36. I have since repeated the experiment with one pile or 1000 series: a spark 
passed between the 'plate and point of the micrometer electrometer through a space 
of J^ths of an inch, but I could not obtain any elfect, even with the entire series, 
on Harris’s thermo-electrometer, or with a delicate galvanometer, or any evidence 
of chemical action*. 
37- Subsequently to the completion of the experiments detailed in this paper, my 
attention was drawn to a paper in the American Philosophical Transactions, entitled 
Contributions to Electricity and Magnetism, by Dr. Henry of Philadelphia, Third 
Series. I have not had the opportunity of seeing the previous series, but find that 
the present investigations of this celebrated experimentalist have been directed to 
the discovery of inductive actions in common electricity analogous to those of gal- 
vanic, and I was in great hopes that Dr. Henry had examined the action of the spark; 
his views, however, appear to me to have been directed to other objects. 
In the twenty-ninth paragraph he alludes to the spark appearing when the ends of 
the second coil were rubbed together; in the thirty-first, that by uniting a number of 
coils the brilliancy of the spark was much reduced ; and in the ninety-sixth, to the 
fact of the induced current in an adjoining conductor being more powerful than in 
the first, and that to render the spark visible, the electricity must be projected through 
a small distance of air: the following experiment was suggested by those of Dr. 
Henry. 
38. Five cells of Professor Daniell’s constant battery were charged and connected 
with the electro-magnetic machine (22.) ; the primary coil of the apparatus (29.) was 
connected with the secondary wire of the machine (22.), and the micrometer elec- 
trometer (12.) to the secondary wire or coil of the apparatus (29.) ; the armature of 
the machine rotated, but no spark appeared even through g^- 0 th of an inch, although 
slight shocks could be perceived ; but when the secondary coils of both instruments 
(22. 29.) were connected together, a minute but brilliant spark passed at the break 
of the primary wire of the apparatus (29.) through g^tii of an inch. 
It is not my intention to intrude any theoretical opinions of my own, but I will 
* I have since repeated the experiments as to the evidence of chemical action with great care, and after 
many trials have at length been enabled to obtain chemical decomposition of a solution of iodide of potassium 
in the following manner. I fastened about two inches of platinum wire to each end of the pile of 10,000 series ; 
the two points were approximated parallel to each other, about a quarter of an inch apart ; a piece of bibulous 
paper, saturated with a solution of iodide of potassium, placed on a slip of glass, was then brought into contact 
with the ends of the wires, and the iodine invariably appeared on that attached to the end of the pile termina- 
ting with the oxide of manganese. — Nov. 1 9th, 1839. 
