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Physics. — “Further experiments with liquid helium. C. On the 
change of electric resistance of pure metals at very low tem- 
peratures etc. IV. The resistance of pure mercury at helium 
temperatures.” By Prof. H. KAMERLINGH OnNEs. Communication 
ATa AAL a ™* 
on the analogy of the platinum measurements. Within the limits of 
experimental error, which are indeed greater for the present experiment 
than was the case for the others, that value is now supported by 
direct measurement. The conclusion that the resistance of pure gold 
within the limits of accuracy experimentally obtainable vanishes at 
helium temperatures is hereby greatly strengthened. 
$ 3. The resistance of pure mercury. The third most important 
determination was one of the resistance of mercury. In Communi- 
