50 PROFESSOR C. G. KNOTT ON MAGNETIZATION 
corresponding changes in \* were 0°0909/20°3015 and 0°2627/30°5125. Thus we 
find by equation (4) :— 
im We 
0909 BBD x 2 : 
A Opa ee cal oe AD = 0025 ; 
/ 20°3015 x 3089 64:45 a 
ioe 
='00703. 
Notice that in I. (1), II. (1) and (2), the deflections are really double the true values, 
whereas in I. (2) the deflection is given at once. For in the last case the approximate 
balance is altered by the magnetizing force being put on. In the other cases the 
deflections are due to the reversal of the current supplied by the single cell in the © 
battery branch of the Wheatstone Bridge. 
The two cases here given in detail prove that there can be no doubt as toa 
difference of effect under apparently similar magnetic conditions. The nickel wires 
used in the experiments were cut originally from the same piece of wire. The only 
difference between the two forms of apparatus lay in the manner of winding. In the 
first small anchor-ring the nickel core was a small compact closely-wound coil of twenty 
windings of silk-covered wire; in the second large anchor-ring the nickel core was a 
loosely-wound coil of some 10 or 11 turns, with asbestos paper interwoven. It is possible 
that in the compactly-wound coil the inner turns were screened from the full magnetic 
action of the applied field by the outer windings. This view receives some corrobora- 
tion from the manner in which the discrepancy established by the figures given above 
diminishes as the temperature rises. Taking the ratios of the corresponding changes 
in I]. and I. we get the following results :— 
| | Ratio of Resistance Changes (II : I) at 
| Field. 
| 12°-15° Gyan) 93°"D 
| tar) ; 
4 30 2°58 2-01 1-60 
| 92 2°85 2°33 1:83 
14 3°13 2°65 2°12 
Thus the measured effect in the earlier experiment deviates more from the same 
effect in the later experiment the lower the field and the lower the temperature. But 
this is just what would be expected if the discrepancy were due to magnetic screening, 
which is well known to become less evident in higher fields. There are no experiments, 
so far as I am aware, as to the effect of temperature on the screening effect; but 
we have every reason to expect that it will diminish as the temperature rises. ‘The 
* In the earlier paper A was called m ; its value was less than the value of A in the present paper. 
