I 207 ) 



manner as those of the rods in the vacnimi glass. Now we have 

 taken only a double glass filled with wool, enveloped in a card-board 

 funnel and tube for letting out the cold vapours. 



The measurements are given in table III. 



The ).'s found in the experiment are of the same order of magnitude 

 as those found with the long rods. The calculation with the coefficients 

 a and b found in § 2 yields : 



Ly^o = 227,547 while we have found Ly^o = 227,544 

 Lo, =227.487 „ „ „ „ Lo, =227,488. 



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

 Jolles and Miss A. Sillevis for their assistance in this investigation. 



Physics. — ■ "On the measurement of very loio temperatures. XI. A 

 comijarlson of the platinum resistance thermometer loitli the 

 hydrogen thermometer" By Prof. H. Kamerijngh Onnes and 

 J. Clay. Communication N°. 95^ from the Physical Laboratory 



at Leiden. 



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



§ 1. Introduciion. The following investigation has been started 

 in Comms. N°. 77 and N". 93 YII of B. Meilixk as a part of the 

 more extensive investigation on the thermometry at low temperatures 

 spoken of in Comm. N°. 95^^. In those communications the part of 

 the investigation bearing on the electrical measurements was chiefly 

 considered. 



The hydrogen thermometer was then (comp. Comm. N°. 93 § 10) 

 and has also this time been arranged in the same way as in Comm. 

 N". 60. Afterwards it appeared, however, that at the time the thermo- 

 meter did not cojitain pure hydrogen, but that it was contaminated by 

 air. The modifications which are consequently required in tables 

 V and YI of Comm. N°. 93 and which particularly relate to the very 

 lowest temperatures, will be dealt wiili i]i a separate communication. 



Here we shall discuss a new comparison for which also the filling 

 with hydrogen has been performed with better observance of all the 

 precautions mentioned in Comm. N". 60. 



We have particularly tried to pro\'e the existence of the point of 

 inflection which may be expected in the cur\'e (comp. § 6) represent- 

 ing the resistance as a function of the temperature, especially with 

 regard to the supposition that the resistance reaches a minimum at 

 very low temperatures, increases again at still lower temperatures 

 and e\en becomes infinite at the absolute temperature (comp. 



