ON THE MEASUREMENT OF MAGNETIC HYSTERESIS. 
103 
§ 79. The second specimen was a single iron wire 47 centiins. in length, and 
•00412 scp centim. in section. The magnetising solenoid was that described in § 75, 
and thus the applied magnetic force was practically uniform over the whole length 
of the wire. We examined the polarity of the eastern end of the wire at every 
stage by means of a small compass. We show the results of the experiment in 
figs. 21, 22, and also in the following table, where the last column indicates the 
polarity of the eastern end. It will be seen that the polarity of the end of the wire 
agrees in every case with that corresponding to the direction of the induction at the 
centre of the wire. In fig. 21 the straight line tlirough the origin rejDresents 
2BA/47rZ~, the demagnetising force corresponding to uniform magnetisation, H in 
these experiments being negligible in comparison with B. 
