( 670 ) 
, . . u 22&00 
For the stronger spring these corrections are multiplied by 2 6 1 Q O O ’ 
they are very small. Direct measurements have shown that the values 
calculated in this way are correct, which indicates that the inherent 
magnetism of the carrier is not changed by the various ojierations 
of mounting. 
There is still a correction to be applied to the couple-ratio for the 
change in elasticity of the steadying wire under the carrier when 
its temperature changes from ordinary to that of liquid hydrogen. 
To obtain that correction the ratio of the torsion modulus of the 
platinium iridium wire and that of the weaker of the phosphorbronze 
springs was measured at the two temperatures. This was done in an 
apparatus similar to the one we have described with the exception 
that the cap D could turn relatively to the cover. By a mirror 
method the position of the cap was read on a scale at a distance 
of 175.9 cm. The cap was turned through an angle of about 360°, 
and the exact measurement of the angle was obtained from the same 
scale. This angle is the sum of the torsions of the spring and the 
wire caused by the same couple. The torsion of the wire was read 
from the mirror of the holder. In this way the ratio of the modulus 
of the wire to that of the spring was found to be 
0.0125 at ordinary temperature 
0.0144 in liquid hydrogen. 
The fourth decimal is uncertain; hence the correction is two 
thousanths for the weak spring and two ten-thousandths for the 
stronger. The temperature coefficient of the phosphorbronze spring 
was obtained from determinations of the period of oscillation of the 
same oscillating system while the spring was first at the ordinary 
temperature and then surrounded with steam. By means of the 
temperature coefficient thus determined viz.: 
— 0,00053 
the observations are reduced to the same temperature. 
The temperature of the liquid bath in the vacuum tube was proved 
to be constant to 0,1 degree, by carrying out temperature measure¬ 
ments with a platinum resistance thermometer placed at different 
heights in a similar vessel. When placed alongside the thermometer 
it indicated temperatures corresponding with those deduced from 
the vapour pressures. 
Capillary action in the oil damper. 
Care was taken to fill the oil vessel to such a height that the 
cy in nca ring carrying the vanes of the damper was partly immersed 
