(213) 



In those cases where the W — R have been derived f^om two deter- 

 minations the values in the 2""^^ column are marked with an * ^). 



If we derive from the differences between the observed and 

 the computed values as far as — 217° the mean error of an obser- 

 vation by means of Aj, this mean error is expressed in resistance 

 ± 0,025 i2, in temperature ± 0^^,044. 



The mean error of an observation of the hydrogen thermometer, 

 as to the accidental errors, amounts to 0°,02 corresponding in resist- 

 ance to ±0,010 i2, while that of the determination of the resistance 

 may be left out of consideration. We cannot decide as yet in how 

 far the greater value of the differences between the observations and 

 the formula is due to iialf systematic errors or to the formula. 



For the point of inflection in the curve representing the resistance 

 as a function of the temperature we find according to B — 180° "). 



In conclusion we wish to express hearty thanks to Miss T. C. 

 Jolles and Mr. C. Braak for their assistance in this investigation. 



Physics. — "On the measurement of very loio temperatures. XII. 

 Comparison of the platinum i^esistance thermometer ivith the 

 gold resistance thermometer. By Prof. H. Kamerlingh Onnes 

 and J. Clay. Communication N°. 95'^ from the Physical labora- 

 tory at Leiden. 



(Communicated in the meeting of June 30, 1906). 



§ 1. Introduction. From the investigation of Comm. N°. 93, Oct. 

 '04, VIÏI it was derived that as a metal for resistance thermometers 

 at low temperatures gold would be preferable to platinum on 

 account of the shape of the curve which indicates the relation 

 between the resistance and the temperature. 



Pure gold soems also better suited because, owing to the signifi- 

 cation of this metal as a minting material, the utmost care has been 

 bestowed on it for reaching the highest degree of purity and the 

 quantity of admixtures in not perfectly pure gold can be exactly 

 determined. The continuation to low temperatures of the measurements 

 described in Comm. N". 93 VIII — which had to be repeated 

 because, although Meilink's investigation just mentioned had proved 

 the usefulness of the method, a different value for the resistance 



1) The deviations of the last two lines differ a little from the original Dutch 

 paper. 



2) Owing to e being negative [B] gives no minimum; a term like that with e 

 does not contradict, however, tiie supposition ?<; - go at T — (§ 1) as the foimula 

 holds only as far as — 259''. 



15 



Proceedings Royal Acad. Amsterdam. Vol. IX. 



