"904 Mr. A. H. Davis on the Beat Loss by 



special chamber. Table I. is calculated from the data given 

 in table iii. of their paper. As before, allowance has been 

 made for variation of k and v with temperature. It has 

 been assumed that, as indicated by the kinetic theory of 



Table I. 



Convection at various air pressures. 



Wire diam. 0*0114 cm. y = 970 cm. per sec. 



Values of v given for a pressure of 1 Atmosphere 



( = 1*012 xlO 6 bars). 



Room temperature about 20° 0. 



Pressure 



(bars). 



390° O. excess. 

 log v= 1-56 



log & —5'95 



538° C. 

 logv- 

 log£= 



excess. 



:T67. 



=4-00. 



10 6 X 



log vl/v. log H/&. 



log vl/v. 



logH/£. 



4-0 





— 



1-97 



1-33 



3-95 



2-07 



1-36 



— 



— 



2-02 



— i — 



1-68 



118 



2 00 



1-78 | 1-20 



— 



— 



1-02 



1-48 T08 



T38 



1-05 



044 



112 0-92 



j 



101 



0-90 



gases, both the conductivity A; of a gas and its viscosity 7} 

 are independent of pressure. The kinematical viscosity v has 

 consequently been taken as inversely proportional to the 

 pressure of the gas. The data of Table J., if plotted on 

 the graph of fig. 1, agree satisfactorily with the curve there 

 given for air at atmospheric pressure. A slight upward 

 displacement above the line occurs for all the points, but this 

 is undoubtedly due to experimental error, since two of the 

 points relate to ordinary atmospheric pressure, and should 

 agree with King's results for the same condition. 



It is interesting to compare the above results for air with 

 data for the heat loss in a stream of other fluid. Worthington 

 and Malone * have shown that the convection of heat from a 

 0*0256 cm. platinum wire in water follows the same laws as 

 convection in air. Water carries off over 100 times as much 



* J. Frank. Inst, clxxxiv. p. llo (1917). 



