190 MR. GASSIOT ON THE POSSIBILITY OF OBTAINING A SPARK 
outer circle, the secondary wires ; at A, A' are binding screws, by which the connex- 
ions may be made with the primary wire to the battery (17.), and at B, B' similar 
screws attached to the terminations of the secondary. 
30. The primary coil (29.) being introduced in the circuit of a battery of twenty of 
the large cells (17 -)j and connexion made from the secondary coil to the pillars of the 
micrometer electrometer (12.), whenever the connexion with the primary wire was 
broken, a spark passed through a space of g^ths of an inch ; but no effect could be 
observed on the liquid in Harris’s thermo-electrometer (25.), until a bundle of iron 
wires was introduced in the centre of the helix, when the liquid rose 3°. 
31. When two galvanometers are introduced, one in the circuit of the primary and 
the other in that of the secondary wire, the deflections of the needles will indicate 
currents in opposite directions. This action was noticed by Dr. Faraday in some of 
his earliest Researches*. In the course of these experiments I however repeatedly 
observed that no effect could be obtained on an exceedingly delicate galvanometer 
introduced in the circuit of the secondary wire, unless it was completed by actual con- 
tact. I introduced two galvanometers, one A, in the circuit of the primary, and the 
other B, in that of the secondary ; when the ends of the latter were approximated to 
within g^oth of an inch, the spark appeared whenever the contact with the primary 
was broken, but without producing the slightest action on the galvanometer B, the 
needle A of course being acted on in obedience to the direction of the current. 
32. Although I had succeeded in obtaining a distinct spark through an appreciable 
and measured space (16. 23. 24. 26. 30. 31.), still the effects could only be assumed 
as due to some secondary cause; for while with 100 series of Professor Daniell’s 
powerful constant battery the spark could not pass through a space occupied by a 
single thickness of a silk handkerchief, yet with the apparatus (22.), a single pair, as I 
afterwards found, was sufficient to produce the spark. 
33. In the next series of experiments, I used an apparatus of a very different de- 
scription to those I have described, one which, although well known to every elec- 
trician, has been very little used in this country; I allude to the pile of Zamboni. The 
one I have consists of a 10,000 series of laminated zinc, paper, and oxide of man- 
ganese, each disc being about one inch in diameter : this pile was divided into ten 
separate piles of 1000 series each. 
34. With this apparatus, using the micrometer electrometer, 1 obtained distinct 
sparks through a space of ^th of an inch, when the two balls were used, one being 
connected by wires to each end of the pile ; and when points were fixed to the pillars the 
sparks passed through foth of an inch. At ^th the stream of sparks was so powerful 
as to produce that peculiar phosphorescent odour which is always perceptible in the 
action of the electric machine, or in the gases evolved from the decomposition of 
water by the voltaic battery. 
35. A Harris’s unit jar was introduced in the circuit, a wire from one end of the 
* Philosophical Transactions, 1831. 
