RESEARCHES IN MAGNETISM. 
573 
The following observations, made with another piece of annealed iron wire at a part 
of the curve very sensitive to the actions now spoken of, show well the reduction 
of range by reversals and then the rise of magnetism, induced and residual, produced 
by successive removals and re-applications of <§. This last occurs in a very marked 
way after the range of magnetic change has been reduced by reversals of <§. The 
two directions of the current will for brevity be distinguished as A and B. The 
changes were sudden, and the magnetism was determined by the direct magnetometric 
method. A want of symmetry is very noticeable here between the positive magneti¬ 
sation due to the current A, which is first applied, and the subsequent negative 
magnetisation due to the equal and opposite current B. 
Magnetometer. 
Made A . 
+ 232 
„ B. 
-110 
> 
„ A . 
+ 180 
„ B. 
-101 
..A . 
„ B. 
+ 172 
-100 
Diminution of range by reversals. 
Twenty reversals, then— 
Made B. 
- 95 
„ A . 
+ 158 
, 
Broke A . 
+ 150 
Made A .. 
+ 200 
Broke A . 
Made A . 
Broke A . 
+ 193 
+ 206 
+ 201 
Rise of magnetism (induced and residual) 
- by successive removals and re-applications 
of h- 
Twenty makes and breaks, then— 
Broke A . 
+ 205 
Made A . 
Then reversals again— 
+ 209 
Made B. 
-105 
„ A . 
+ 178 
The diminution of range by reversals is 
Forty reversals, then— 
again conspicuous. 
Made A . 
+ 163 
„ B. 
-105 
J 
Broke and remade B. 
-136 
Ditto twenty times. 
-175 
Further experiments with the same wire showed, after the range was reduced by 
reversals, that a gradual removal and re-application of produced, though to a much 
less degree, the same effect as a sudden removal and re-application ; the effect, 
namely, of increasing the magnetism. 
§ 58. The magnetisation of steel exhibits, even more than that of iron, reduction of 
range with successive reversals of >§, and want of symmetry between the values of 3 
induced by successively applied fi- and — values of <§. Plate Gl, fig. 28, shows the 
changes of magnetism which were undergone by an annealed steel wire when a 
magnetising force of 15 c.g.s. units was applied, removed, re-applied, reversed, and 
re-reversed twice. The want of symmetry between the positive and negative values 
MDCCCLXXXV. 4 E 
