4G0 
DR. J. HOPKmSOK- ON MAGNETIC AND OTHER PHYSICAL 
When cold, the resistance of the secondary coil and leads was 0'768 ; in calculating 
the temperatures, it is assumed that the cold resistance is 0'7G8. It is obvious that 
there is here considerable uncertainty concerning the actual temperatures, owing to 
the chanofes in the condition of the wire due to its oxidation. 
The following series was next made, the mean results being given in 
Table 34, Curve XXVI. 
Magnetising force. 
Galvaiiometer kick. 
Resi.stance in circuit. 
Induction per sq. cm. 
0-065 
29 
1-198 
10 
0-13 
58 
1-198 
19 
0-26 
120 
1-198 
40 
0-52 
251 
1-198 
83 
1-04 
66 
11-198 
203 
3-74 
170 
21-198 
991 
6-03 
159 
101-2 
4,420 
9-78 
283 
7,867 
13-94 
176 
201-2 
9,733 
15-81 
187 
10,341 
22-67 
211 
11,668 
The ring wns now demagnetised, and another series of determinations was made, 
the mean results being given in 
Table 35, Curve XXVIl. 
Magnetising 
force. 
Galvanometer 
kick. 
Resistance in 
circuit. 
Induction per 
sq. cm. 
0 065 
26 
1-198 
9 
0-13 
54 
18 
0-26 
111 
37 
0-52 
236 
78 
1-04 
60 
11-198 
185 
2-08 
132 
407 
3-74 
327 
1,007 
6-24 
130 
101-2 
.3,614 
9-78 
265 
7,367 
13-10 
168 
20 L-2 
9,290 
15-7 
187 
10,341 
22-67 
211 
11,668 
Comparing Curves XXV. and XXVIl., we see the effect of annealing the iron to be 
to increase its permeability. Comparing Curves XXVI. and XXVIl. we see the effect 
of demagnetising by reversed currents. Curve XXXIV. shows the relation of perme¬ 
ability to temperature for a force of 1‘5. 
Mmigancse Steel .—The sample of this steel was given to me by Mr. Hadfield, 
who also supplied me with the following twm analyses of the sample ;— 
