355 



over a wider range lliaii luiglit have been expected according to 

 the kinetic theory. 



R 



In - 



r, 0.250 



It follows from y.n= . y, lliat v ■ l> ^ — 7-; t^t 9^.2 C. 



' ' 1 1 ' .68.44 



when llie |>ressiire p is measured in djne/cm* and / in cms. 

 we tin(i according to 0. E. Mkykr (p. 344) from tiie viscosity 



/7'\l.-2 



pA = J8.93 . 1 -- I . This gives at the temperature ot the wire 



vA = 2.46 



Hence with a ■= 0.653 



2— a 

 •//; = 2.38 . --- . 

 2a 



The agreement is not so close as it was with the value found 

 previously, but the deviation is not larger than can be explained 

 by accidental errors. 



It appears from tiie table that )\ changes with the temperatuie ; 

 this was to be expected as X depends on the temperature according 



to the relation ;. = ^.^ . I — 1 . Calculating the values ot )\ whicli have 



to be expected at the various temperatures, the results y^ rah-., given 

 in cohimn 3 are obtained. On comparing these with the experimental 

 results the latter are seen to change more rapidly with the tem- 

 perature. This can be explained by the assumption that the accom- 

 modation-coefticient a is not independent of the temperature. The 

 same assumption is also rendered probable by the results for hydrogen; 

 Knudsen ^) found that in this case a had a negative temperature- 

 coefficient — 0.001. Assuming the value — 0.00076 for the teniperature- 

 coefficient of a foi neon we find for y, the results given in 

 column 4 under y^rair.- 



§ 6. By the aid of the principle of "similar motions'" as given by 

 H. Kamkri.ingh Onnes ') a comparison may be made between the 

 heat conductivity of different substances for which the conduction 

 through the molecides themselves may l)e disregarded. It is found 

 that at equal reduced temperatures we must have: 



1) M. Knudsen. Ann. d. P'l. (4) 34, (1911) p. 632. 



5) H. Kamerlingh ÜNNErf. Verh. Kon. Akad., 21, p. 22, 1881. 



