RESEARCHES IN MAGNETISM. 
551 
Ergs. 
(4) For the large cycle of fig. 6 (§22), produced by the double reversal of 
magnetisation in a piece of annealed iron wire similar to the above, 
but between higher limits of magnetising force, namely, from .§ = 90 
to —90, and back, the value of is. # 16,700 
(5) For the upper small loop of fig. 6, produced by removing and 
restoring the magnetising force of +90, the value of J3>d§ is . . 350 
(6) For the cast-iron ring of § 24, fig. 7, the reversal of magnetisation 
from the greatest positive value there produced to an equal negative 
value, and back, gives as the value of |2>d§. 6,100 
This, however, is obviously much less than the energy which would 
be expended in a double reversal of magnetisation in cast-iron, were 
the magnetisation as nearly complete as in the experiments on 
wrought iron and steel. 
The above values of the energy dissipated in producing cyclic 
changes of magnetisation are greatly exceeded when the material is 
steel. 
(7) For the hard-drawn steel wire of § 25, fig. 8, the double reversal of 
magnetisation between the extreme positive and negative limits 
about 14,600, § = 57’5), gives for the value of J2>(7§. . . . 60,000 
And the small loop, for the removal and restoration of § in the 
same experiment, on the positive side, gives. 6,300 
(8) The corresponding quantities in the case of the same steel wire, 
annealed (§ 26, fig. 9), are :— 
For the double reversal.J2>d§ = 70,500 
For the small loop.j2>d§ — 1,800 
(9) A.nd in the case of the same steel wire, glass-hardened (§ 27, fig. 10): 
For the double reversal.J2>d§ = 76,000 
For the small loop.J<3d§ = 700 
In this case, as in the case of cast-iron, the magnetisation was so 
far from “ saturation ” that a comparison of the above values of 
the integral with those of other experiments would be unfair. 
In the three next examples the magnetising force was much 
greater than in the above, and the energy expended in going 
through the cycles was also greater. The measurements are those 
of §§ 28-30, figs. 11, 12, and 13, the material being pianoforte steel, 
and the magnetising force ranged from +100 to —100 nearly. 
* This value was inadvertently given as 1670 instead of 16,700, in a paper read before the British 
Association at Southport (Report for 1883, p. 404), and reprinted in the Phil. Mag. for November, 1883, 
p. 383. 
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