( 119 ) 



we hope to repeat this experimenl kitei- under more favourable cir 

 curastances. 



TABLE IV. 



§ 3. Deductions. Paramagnetic substances. The order of sequence 

 of the three ]>aramagnetic substances has been purposely chosen. It 

 is a striking fact that even down to 17° K. gadolinium sulphate 

 remains in perfect agreement with Curie's law. It first begins to 

 show a slight deviation in the direction of too small a susceptibility 

 in the neighbourhood of the melting point of hydrogen. On the 

 other hand the susceptibility of ferrous sulphate is inverselj' propor- 

 tional to T down to 64° K. In a bath of hydrogen boiling under 

 atmospheric pressure a deviation in the direction of a decrease is 

 quite clearl}^ noticeable, and this deviation increases rapidly as the 

 freezing point of hydrogen is approached. And finally dysprosium 

 oxide even between ordinary temperature and 170° K. shows a 

 deviation of 4 7o which gradually increases so far that in liquid 



c 

 hydrogen the susceptibility is only one half of - . Let us conclude 



our list by the addition of oxygen, remembering that this substance 

 as well as ferrous sulphate and in all probability the two rare earths, 

 too, follow Curie's law at ordinary temperatures, and we can only 

 conclude that probably the susceptibility of substances which obey 

 Curie's law at ordinary temperatures will, in general, if the tempe- 

 rature be sufficiently lowered, increase more rapidly than they should 







in accordance with the — formula, but that the individual tempera- 



1) Gf. Suppl. m. 2 to Nos. 61—72. 



