(-4852 ) 
riments towards obtaining data for magnetization in strong fields, 
and from these the deduction of the law according to which the mag¬ 
netization approaches its limiting value. But the method chosen for 
the magnetic measurements, viz: the determination of the maximum 
value of the couple exerted by a magnetic field of varying direction 
upon an ellipsoid of the experimental substance, was, as we shall 
presently show, less suitable for this determination of the law of 
approach than for comparisons of the magnetizations of the substance 
in the same field at different temperatures. The data to determine 
the law of approach were therefore made the subject of a separate 
investigation *) This gave the following values for the difference 
between the magnetization in a field of 10000 gauss and that in the 
limiting case: 
Iron 0.08 °/ 0 
Nickel 0.1 „ 
Cobalt (soft) 1.1 
Magnetite 0.19 „ 
For these substances, the cobalt excepted, the approach of magneti¬ 
zation as a function of the strength of the field is hyperbolic, so that 
in a field of 20000 gauss, which we reached in our present experiments, 
the above differences were reduced to half their values. Observations 
by the ellipsoid method in different fields and at both low and 
ordinary temperatures have not, indeed, enabled us to > test the law of 
approach, but they show sufficiently, well that there is no essential 
difference between the behaviour in this respect at the two temperatures; 
and that at low temperatures, as could have been supposed the 
magnetic hardness does not assume an excessive value, the molecules 
hindering each other in assuming a new direction. 
Further, by means of comparative measurements, magnetizations 
at ordinary and at low temperatures in fields of great strength were 
compared, and it was found that the ratio between the two is pretty 
well independent of the strength of the field. Thus, leaving the 
result uncorrected for the dilatation between the two temperatures 
(see note 2 on p. 11 ) we found for the ratio of the intensity of 
magnetization at 2(F,2 K. and at ordinary temperature the following: 
Nickel (17°.3C.) 1.0548 
Iron (20" C.) 1.0210 
Magnetite (15°.5 C.) 1.0569 
The exact value of the ordinary temperature is given between 
bracke ts. In $ 5 n will be explained why the experiments with 
i) p . W*iss Arch, des Sc. phys. et nat. fevrier 1910 andJourn.de Phys. 4eS£r. 
t IX. avnl 1910. , 
