1911-12.] Transverse Induction Changes in Demagnetised Iron. 305 
and circular induction (continuous curve), and by the ratios of the longi- 
tudinal and circular residual magnetisation (broken curve), at a sufficient 
number of stages. Between B = 15,000 and 8000 demagnetisation is pro- 
ceeding at a less angle than the calculated value of 0 — 7l°*6, at lower 
values than B = 8000 at a higher angle. The same result holds for 
<9 = 63°-5 and 80°*6. 
The maximum value of each curve of transverse induction change 
(fig. 5) may be plotted radially against the demagnetisation angle. The 
continuous line curve (fig. 7) shows the experimental result for the 
calculated angles 0, the dotted curve given by sin 0 cos 0, symmetrical 
in the quadrant, being added for comparison. But the angle of demagnet- 
isation does not remain constant during the process for the three higher 
angles. What each stage contributes to the demagnetisation is unknown. 
If it could be assumed that the decreasing reversals between B = 15,000 
and 8000 have a less effect on the maxima of the various curves than 
reversals at lower values, the result would be more symmetrical, the 
dash-line curve taking the place of the continuous curve for 0 = 6 3°*5, 
7l°*6, and 80°-6. 
Reverting again to fig. 5, it may be observed that the curves closely 
resemble differential permeability (dB/dH) curves. B — H induction curves 
were plotted for the various angles of 0, but they are not here reproduced, 
their co-ordination with the transverse effects not being pursued in this 
communication. It may be stated, however, that for low values of H 
the co-directional induction B c is first delayed, afterwards accelerated the 
closer the demagnetisation angle approximates to 0 = 90°. Under the same 
conditions the transverse curves are more peaked for the higher than the 
lower angles of 0 • When plotted against B c these differences are not 
obvious. 
(2) Theoretical. 
The co-ordination of the above experimental results with the hypothesis 
advanced will now be attempted. 
The various diagrams of fig. 8 show the results calculated by the 
methods already indicated. The ordinates represent the changes of the 
vertical (transverse) components of the molecular moments in terms of 
the summations of the products of sines, as illustrated by the table on p. 297. 
The abscissae (positive field) have the same signification as in fig. 2. 
Diagrams (1) to (5) show the results calculated for double parallels of 
latitude as marked on each diagram. They represent the contributions 
VOL. xxxii. 20 
