1071 
tioned old steel magnet e.g. amounted to 12,9°/,, near the middle 
however to §,5°/,; for a magnet of hardened steel the change near 
the end was 2,1°/,, at a distance from the end equal to 4 of the 
length 1,2°/,. In both cases the coefficient « was positive. For a 
bundle of piano-strings which each had a diameter of 1,2 mm and 
a length of 17,5 em the change between 20° and 100° was —3,9°/, 
at the end and — 6,1°/, at a distance from the end equal to 4 of 
the length. After partial demagnetisation, by which the magnetisation 
was diminished to 4 of its original value the change between the 
same temperature limits at the end was only — 1,5 °/,. Magneto- 
metrically (now we are principally concerned with the action of the 
end of the magnet) there was found before the demagnetisation SoMa 
and afterwards —1,6°/, (here the temperature limits were 10° and 
100°). From this we might conclude that for steel the coefficient « 
depends on the magnetisation in this way that it increases in the 
positive sense according as the latter decreases. This agrees with 
what was found in the investigation of different parts of one and 
the same steel magnet, viz. that near the end « is greater in the 
positive sense than in the middle; for because of the demagnetising 
force the magnetisation at the ends is much smaller than in the 
middle. 
December 1915. Physical Laboratory of the 
Teyler Institute. 
Physics. — “Some remarks on the hydrogen-molecule of Bour — 
Deere.” By Miss H. J. van Lesuwen. (Communicated by 
Prof. H. A. Lorentz). 
(Communicated in the meeting of December 18, 1915). 
$ 1. Bour has been the first who supposed the hydrogen-mole- 
cule to be formed by two nuclei which carry a positive elementary 
charge and in which nearly the whole mass of the molecule is 
concentrated, together with two electrons which in the normal state 
circulate with a constant angular velocity diametrically on a circle 
that has its centre in the middle between the nuclei and its plane 
perpendicular to their line of connection, the “axis” of the molecule *). 
Bour supposes that such molecular systems do not obey the laws 
of classic mechanics, that on the contrary all motions of the electrons 
are bound by the condition that for each single electron the moment of 
') N. Bonr. On the constitution of atoms and molecules III, Phil. Mag. 6, 26, 
1913 p. 857. 
