154 ME, W. CROOKES ON THE ILLUMINATION OF LINES OF 
546. The induction current being turned on, the shadow of e is projected straight 
along the tube in the position f e, g e ; the edge of the shadow f is called the zero 
position, marked 0 on fig. 16, A. The electro-magnet is now excited by 1 cell. The 
shadow is deflected sideways to the position shown by 1, p, the edge f e now moving 
to 1, and the edge g e moving to p e. The lines f e and g e, when under no magnetic 
influence, are marked along the bottom of the bulb by perfectly straight lines, but when 
deflected by the magnet they are curved as at 1 e, p e. 
On increasing the number of cells actuating the electro-magnet, the deflection of the 
shadow likewise increases. Thus, the following is the deflection of the edge f e under 
varying magnetic force :— 
No. of cells. 
Position on 
drawing. 
(Fig. 16, A.) 
Distance deflected, 
measured from 
zero, or/. 
millims. 
o 
fe 
0 
1 
1 
6 
2 
2 
10 
3 
3 
13 
4 
4 
16 
5 
5 
17-7 
547. The width of the deflected shadow varies in like manner with the magnetic 
force, as seen by the following table 
No. of cells. 
Width of shadow, 
measured along the 
side of the bulb. 
millims. 
0 
39 
1 
24 
2 
17 
3 
13 
4 
10 
5 
7'5 
With 3 cells the position of the shadow is shown at l m in fig. 16, plan, shaded from 
left to right by diagonal lines, and with five cells the shadow is in position n o, indi¬ 
cated in the figure by horizontal lines. The position of the shadow when not under 
magnetic influence is represented by diagonal lines running from right to left. 
