352 



IV D' =^ D — R, where R is the radiation (as Li is not quite 

 constant, D — R has been rednced to the same temperatnre-diiference) 

 and column V D'^o,,. arising bj the correction of D' for tiie 

 temperatnre-drop at the wall. The latter correction is made by the 

 formula (com p. formula IV on p. 346) : 



1 1 



i>',,,, = X>' ( 1 4 ^ 



Pan 



, where y, = 



R'^r. 



In 



R 



ypc 



With the differences of temperature which are used we ma}' 

 assume with sufficient accuracy, that K corresponds to the temper- 



^< , 

 ature LH ; hence we have: 



Atm. air: 7' = 273.1 4- 8.75 • DVon. = 0.0004371 



neon: „=273.1 -j- 4.60 „ =0.0008218 



„=273.1 -+-99.81+6.00 „ =0.0010071 



„=194.72+ 4.01 „ =0.0006602 



„= 89.90 -f 1.77 „ =0.0003740 



Hence taking the temperature-coefficient of the conductivity for 



air as 0.0033, the following results are obtained : 



Atm. air: 7' = 273.1 1)^ = 0004248 



neon: 7= „ „ =0.0008135 



For the conductivity at 0° C. ^) of dry air free of carbon dioxide 

 1 have found A'^ = 0.00005680 ; using this value K\ for neon is 

 found as follows: 



8135 



K\ =-^-_ . 0,00005680 = 0.0001087 ^'■'''^■/sec.yrad.cm. 



= 1089.10-^ 



4248 



in good agreement with my previous determination TT/ 



This result shows that the two calibrations of the apparatus are 

 in good mutual agreement; the following results are now obtained 

 for neon : 



1) S. Weber. Ann. d. Phys. (4) 54. (1917), p. 352. 



