Electro-Magnetic Experiments. 407 
through the helices attached to the battery and while in this state 
one of its ends was quickly introduced into the helix connected with 
the galvanometer ; the deflection of ihe needle, in this case, was sev- 
en degrees. ‘Lhe end of the rod wasnext introduced into the same 
helix while in its natural state and then suddenly magnetized ; the de- 
flection, in this instance amounted to thirty degrees, shewing a great 
superiority in the method of induction. 
The next attempt was to increase the magneto-electric effect while 
the magnetic power remained the same, and in this | was more suc- 
cessful. Two iron rods six inches long and one inch in diameter, 
were each surrounded by two helices and then placed perpendicu- 
larly on the face of the armature, and between it and the poles of the 
magnet so that each rod formed as it were a prolongation of the poles, 
and to these the armature adhered when the maguet was excited. 
With this arrangement, a current from one helix produced a deflection 
of thirty seven degrees; from two helices both on the same rod fifty 
two degrees, and from three fifty nine degrees: but when four 
helices were used, the deflection was only fifty five degrees, and 
when to these were added the helix of smaller wire around the 
armature, the deflection .was no more than thirty degrees. This 
result may perhaps have been somewhat affected by the want of 
proper insulation in the several spires of the helices, it however 
establishes the fact that an increase in the electric current is 
produced by using at least two or three helices instead of one. 
The same principle was applied to another arrangement which 
seems to afford the maximum of electric development from a 
given magnetic power ; in place of the two pieces of iron and the 
armature used in the last experiments, the poles of the magnet were 
connected by a single rod of iron, bent into the form of a horse-shoe, 
and its extremities filed perfectly flat so as to come in perfect con- 
tact with the faces of the poles: around the middle of the arch of 
this horse-shoe, two strands of copper wire were tightly coiled one 
over the other. A current from oue of these helices deflected the 
needle one hundred degrees, and when both were used the needle 
was deflected with such force as to make a complete circuit. But 
the most surprising effect was produced when instead of passing the 
current through the long wires to the galvanometer, the opposite ends 
of the helices were held nearly in contact with each other, and the 
magnet suddenly excited; in this case a small but vivid spark was 
seen to pass between the ends ofthe wires and this effect was re- 
peated as often as the state of intensity of the magnet was changed. 
