620 
PROFESSOR J. A. EWING ON EXPERIMENTAL 
the field was raised to values considerably greater than those of preceding experiments 
of this type, chiefly to see whether with very strong magnetising forces the curves 
became convergent. 
A specimen of the iron wire usually employed (079 mm. in diameter and 33 cm. 
long), was annealed and subjected to a magnetising force which was gradually 
increased to 97'9 units, first with a load of one kilo, on it, and afterwards (after 
demagnetisation by reversals) with a load of 6 kilos. The results are given in 
the table below, reduced to absolute measure. The same wire was then stretched 
(in a non-magnetic state, and in a neutral field) by applying a load of 15 kilos., giving 
an elongation of 2‘2 cm., and was again magnetised, successively in two different 
conditions, namely, with no load and with a load of 8 kilos. The load of 8 kilos, 
was selected because previous experiments had shown that with moderate magnetising 
forces the susceptibility is greater under 8 kilos, than under any other load. At 
the same time the earlier experiments had shown that as the magnetising force 
was increased, the load giving maximum susceptibility became less and less, and 
therefore had made it likely that the 8-kilo, curve would be found to cross and run 
under the normal or no-load curve when the magnetising force was greatly 
heightened. The results of the present experiment, which are stated below, confirmed 
this expectation. 
Magnetisation of Iron in a strong field under constant loads, Plate 66, fig. 55. 
Before stretching (soft annealed state). 
Load = 1 kilo., 
or 2’04 kilo, per sq. mm. 
3. 
Load = 6 kilos., 
or 12 24 kilos, per sq mm. 
3. 
0 
0 
0 
2-3 
346 
3T 
595 
441 
4'2 
791 
630 
63 
994 
833 
8-4 
1074 
945 
127 
1137 
1050 
20-3 
1173 
1120 
33-6 
1207 
1169 
48-9 
1239 
1204 
60-9 
1249 
1221 
747 
1260 
1232 
88-6 
1264 
1242 
97-9 
1270 
1246 
0 
1092 
847 
(residual) 
(residual) 
! 
