ELECTEODYNAMIC QUALITIES OE METALS. 
709 
the fii.st M(— ) of Series XXX. gave 22 of increase to the magnetization of the steel 
wire which had remained for six days undisturbed as left at the end of Series XXIX. 
After an “ on ” and “ off” of 28 lbs.* the current was stopped, and the magnetism of 
the wire instantly fell 4-5. A second M(— ) gave 8 of increase to the magnetization, 
while the current was continued, of which 6 was instantly lost when the current was 
stopped a minute or two after. Then M(-j-) without other disturbance produced 161 of 
demagnetization and reverse magnetization, of which 5 was lost when the current was 
stopped a minute or two after, and 5 ’5 more in the set of six ons and offs which 
followed. The residual reverse magnetization must (as we may judge from subsequent 
results of Series XXX. and XXXI.) have been approximately equal to the immediately 
previous residual magnetization remaining from all the previous M(— ) and other opera- 
tions to which the wire had been subjected from the time in November when it was set 
up for the experiments. Subtracting 10J from 161 we find 1504 for the number 
measuring the change from the previous ( — ) magnetization to the equal ( + ) magneti- 
zation in the wire at the present stage of its history. The amount of this magnetization 
is therefore 75^, say 75. With this amount of magnetization in the wire, and 28 lbs. 
hanging constantly on it, the effect of putting on and off another 28 lbs. is to diminish 
and increase the magnetism by 6 ; that is to say, to diminish it and increase it by about 
of its mean value (which, according to these rough estimates, is 7 3 of our arbitrary 
scale). The remainder of Series XXX. speaks intelligibly for itself. 
191. Interpretation of Series XXXI. — The first on gave a diminution 20 in the 
magnetization, the second 13^; the first on and the off, on, off following, gave on the 
whole a diminution of 9-|, that is to say, shook out 9^ of the 75 of the residual mag- 
netism remaining from Series XXX. The effect of repeated ons and offs on the 65-| of 
remaining magnetism would no doubt have shaken but very little more out, and would 
have caused alternate diminutions and augmentations of about 12 ; that is to say, with 
56 lbs. hung on, in addition to the constant 28 lbs., the magnetization of the wire 
would have been 53, and with only the 28 lbs. it would have been 65. 
The M(— ), on, off, and B which actually followed, added .15jr to the magnetization, 
and so brought it up to about 80f, or 5f more than it had at the beginning of Series 
XXXI. The subsequent M( — ) and B probably produced little, if any, further change 
in the residual magnetization ; and the on, off, on which followed confirmed the previous 
result of augmentation 12 and diminution 12, alternately by off and on, after something 
considerable shaken out permanently by the first on. The off, on, off after M( — ) with 
current still flowing gave about 10 instead of the 12 found previously when the current 
was not flowing. These results agree in kind and amount with what was to be expected 
from Series XIV. and XV., considering that “ on” and “ off” in those series was 84 lbs.* 
on and off (with nothing, or only a very slight steadying weight kept always on), whereas 
now the “ on” and “.off” means change from 28 lbs. to 84 lbs. and back. 
192. Interpretation of Series XXXI. continued. — Taking now the effects of Ms and 
* Another weight of 28 lbs. hanging constantly on the wire. 
5 F 
MDCCCLXXVI. 
