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hardness etc. For the present we have left the latter out of account; 

 in the investigation of the influence of the admixtures, however, the 

 influence of the hardness was as much as possible eliminated by 

 our treating the different samples of metals exactly in the same 

 way when comparing them, and by reducing them to the same state 

 of softness. 



The most natural explanation of the whole of the results obtained 

 as yet (in this and the preceding Communication) is to ascribe the 

 deviations for the different wires of one and the same metal to 

 impurities in the metal, which may also come in during the drawing 

 if efficient precautions do not prevent it, and which even in very 

 small quantities exert a very great influence on the changes of the 

 resistance with the temperature. 



The influence of the drawing is altogether lost for mercury, in 

 which it is also easy to ensure uniform distribution of small quantities 

 of admixture. This enhances the importance of the study of this metal 

 for the investigation of the influence of admixture. In the first place 

 we have measured its resistance at hydrogen temperatures which 

 had not yet been determined ; it is given in § 4. It proved that for 

 pure mercury ') the inflection point falls in the region of liquid hydrogen 

 temperatures. This is a drawback for the inquiry into the change of 

 the resistance with the temperature for pure metals. 



Just as the gold wire Any (see § 2), also the silver wire Agi and 

 the platinum wires of the preceding Communication are probably 

 purer than Dewar's wires of the same metals. For bismuth, on the 

 other hand, Dewar has most likely had a purer sample than we. 

 The change of the resistance at hydrogen temperatures for this metal, 

 which had not yet been measured by him, has been given in § 5. 

 The observations for lead for those temperatures, which were still 

 wanting up to now, have been given in § 6. 



The high degree of purity for some of the metals which were 

 at our disposal, and the lower temperatures to which we descended 

 (solid hydrogen evaporating at 2,5 m.m. pressure) render the decrease 

 of the resistance in some cases many times larger than was observed 

 by Dewar. To this it is also owing that we have observed the 

 great influence, which very small changes in the nature of the metal 

 obtain on the change of the resistance at hydrogen tern ueratures. We 

 may account for this by paying attention to the diilerence of the 

 resistance of a wire of pure metal at the temperature T, )\t, with 



l ) Perhaps in connection with the low melting point. Possibly the point of 

 proportionality is first reached for osmium. 



14* 



