8 



Prof. Magnus on the Propagation of Heat in Gases. 



glass in the neighbourhood of C, assumes temperatures which 

 are higher than 15° C. Although the thermometer is protected 

 against rays which proceed from the side above, it is directly ex- 

 posed, to the rays which come from those parts of the side which 

 are lower than the screen. And as these parts of the side receive 

 more rays when the vessel A B is filled with a gas which readily 

 transmits heat (that is, with a better-conducting gas) than if it 

 contains a gas which possesses these properties in a lower degree, 

 the influence of the side must change with the kind of gas, and 

 cannot therefore be proportional to the indications of the ther- 

 mometer. 



In the following Tables the temperatures are given which have 

 been obtained by the use of two different screens in different 

 gases, at different densities. In obtaining these results, I have 

 had the advantage of the careful help of M. Rudorff, who for 

 some time has been engaged in my laboratory. The tempera- 

 tures are counted from that of the surrounding medium, that is, 

 from 15° C. 



Gas. 

 Atmospheric air 



Oxygen 

 Hydroge 



Carbonic acid 





Thermometer with 



Pressure. 



Cork screen. 



Metal screen 



mru 







759-4 



9-6C. 





753-2 





70C. 



741-5 



9-5 





738-0 



9-5 





553-3 



96 





3730 



100 





3560 



101 





194-7 



11-0 





15-3 



11-5 





11-6 



11-7 





11-6 





7-8 



771-2 



9-6 





100 



11-6 





760-0 



130 





763-5 





120 



517-7 



12-5 





195-4 



121 





11-7 



US 





96 



110 





13-8 





8-6 



750-4 



8-2 





765-3 



8-2 





3091 



9-3 





16-4 



11-3 





