66 



KENNELLY-SANBORN— INFLUENCE OF 



[April 24, 



to free convection, the value becomes infinite. If, however, we add 

 30 cm. per sec. to all the wind velocities v, to correct empirically for 

 free convection as described in the paper of 1909, we obtain the 

 values given in the last column VIII, which do not differ greatly 

 from 1,930 ab watts per cm. ° C. and \/v, at all speeds in the table. 



It will be observed that no correction is made for loss of heat 

 by radiation from the test-wire. That is, the linear dissipations in 

 column VI are treated as though entirely due to convection. In our 

 paper of 1909, a correction was attempted for radiation, on the basis 



Wini.-VtUut>i 



^tir sec. 



Fig. 7. Curves of | — j against v, for (9 = 390°. 



of Stefan's formula. Since, however, it has been pointed out by 

 Dr. Langmuir^ that the radiation from platinum according to Hagen 

 and Ruben's formula is only a small fraction of that from a " black 

 body," or perfectly non-reflecting radiator, at the same temperature, 

 the radiation corrections in the case of Table II are nearly all less 

 than I per cent, of the dissipation, and it has therefore been omitted 

 throughout. 



5 "The Convection and Conduction of Heat in Gases," by Irving 

 Langmuir, Proc. Am. Inst. El. Engrs., June 25, 1912. 



