356 

 K^ ^ K. ^ 



where I\ and Th are the critical constants. 



When a comparison is made in this manner by means of the 

 experimental resnits between the condnctivity of helium and argon 

 with that of neon ^), it seems in the mean time as if the reduced 

 heat condnctivity of neon changes in a different manner with the 

 reduced temperature from liiat of argon and helium; in order to 

 obtain more evidence on this point it becomes even more important 

 than before, also in view of J. J. Thomson's theory (that neon would 

 consist of two isotopic elements with molecular weights of 20 and 

 22 respectively), to determine the conductivity of neon at reduced 

 oxygen- and neon temperatures and that of helium at reduced 

 hydrogen-tempei-atures; as was mentioned in the beginning of this 

 paper, it is the intention to cari-y out this research in the cryogenic 

 laboratory at Leiden. 



In conclusion 1 am happy to express my sincere thanks to 

 Dr. Ir. G. Tj. F. Philips for his kindness through which I was 

 enabled to carry out this research. 



I also wish to thank Mr. H J. Michielsen for the excellent manner 

 in which he assisted me in the measurements and the calculations. 



Physical Laboratory 

 of the Philips Incandescent Lamp F'actories. 



1) S. Weber. Ann. d. Ph. (4) 54, (1917), p. 460. 



