LINES OF MAGNETIC FORCE — WIRES OF DIFFERENT THICKNESSES. 
45 
3138. The influence of this lateral conduction (3137-)5 in cases of magneto -electric 
conduction, must be well understood ; otherwise, in the application of the principles 
to investigation, errors will frequently creep in. Their effect may be shown in the 
following instances : — a loop of four wires, 0*048 of an inch in diameter (3136.), was 
passed over the pole of the magnet, and produced a certain result of deflection or 
swing ; when the wires were separated two and two, so as to be half or three-quarters 
of an inch apart, and when, therefore, in moving across the magnetic field, one pair 
went before the others, the effect was less, for the reason already given in the case of 
the copper cylinder (3137.)- When three wires were allowed to go by together, but 
one taken aside a couple of inches, the effect fell very much ; and when that fourth 
one was cut across to prevent the return current in it, the effect of the three rose at 
the galvanometer very greatly, almost equalling the effect of the four when together. 
3139. A loop was constructed of seventy-six equal fine copper wires, each 10*5 inches 
long and 0*0125 of an inch in diameter, and its effect observed when more and more 
of the wires were cut away. As it is the comparison of the smaller numbers of wires, 
one with the other, that is of most value, I will give the averages of each number for 
several observations, in the reverse order in which they were obtained ; and I intro- 
duce the results with larger numbers of wires only for the general purpose of showing 
how the effect passes into that with the cylinder of copper (3137.), the galvanometer 
conductors always being of the same length and thickness. 
o 
1 wire produced an average swing of 8*3 
2 wires produced an average swing of 15*3 
3 wires produced an average swing of 21*8 
4 wires produced an average swing of 27*9 
5 wires produced an average swing of 34*4 
6 wires produced an average swing of 37'8 
8 wires produced an average swing of 50*1 
12 wires produced an average swing of 65*1 
16 wires produced an average swing of 80*5 
26 wires produced an average swing of 118*0 
36 almost swung the needle round. 
46 stronger than the last. 
56 swung the needle quite round. 
66 a little stronger. 
76 stronger: swung the needle freely round the circle. 
Each time that the needle passed 180°, it was returned, that the torsion foree might 
remain the same for every case. 
3140. When the loop of four equal wires (3136.) was employed, so arranged that, 
in respect of the part which passed between the poles, they should be close together 
in one plane, it made no difference in the result, whether that plane was perpendicular 
