( 675 ) 
H (gauss) 
1700 
5675 
13160 
15700 
16940 
18360 
19250 
TABLE VII. 
Iron. 
/ 2 (cm of scale) 
NjfaO’C. T= 20°.3K. 
(H 2 atm. press.) 
95.23 101.98 
.98.47 102.58 
98.65 103.01 
98.91 103.31 
99.04 103.31 
99.08 103.27 
99.06 103.27 
103.25 
for H = 19250 
18360 
16940 
15700 
T = 14°.0 K. 
(H s solidifying) 
101.95 
103.23 
103.25 
1.0209 
1.0210 
1.0209 
1.0213 
/20°,3K . 
/ 20° C. 
mean not corrected for dilatation 1.0210 
In all the iron experiments the zero as deduced by taking the 
mean of readings to right and' left remained remarkably constant. 
As a rule its displacement was only - a few tenths of a millimetre in 
any one series, and 6 mm. in proceeding from one series to another. 
The few measurements at the temperature of solidifying hydrogen 
are sufficient to show that nothing particular happens between 
20° K. and 14° K. 
. Magnetite. 
We have already mentioned that the preparation of magnetite by 
heating the sesquioxide needs an extremely high temperature if one 
wishes to make sure that the last traces of oxygen are removed. A 
first ellipsoid obtained from iron oxide that had been insufficiently 
heated exhibited only little more that one half of the magnetization 
that was expected; it showed, too, a very distinct hysteresis, which 
was about three times as great at liquid hydrogen temperature as 
at ordinary temperature, while in all the experiments with the other 
substances hysteresis phenomena were insignificant. Moreover, the 
magnetization of this substance was the same at ordinary and liquid 
hydrogen temperatures, while between them it reached a maximum. 
These peculiarities were not displayed by a second ellipsoid cut 
45 
Proceedings Royal Acad. Amsterdam. Vol. XII. 
