Currents arising from two fine heated Platinum Wires. 941 



of Shakespeare's katharometer *, it is desirable that the free 

 convection effect should be eliminated as completely as 

 possible, so that the heat transfer from the heated wire is 

 effected, if possible, entirely by conduction through the 

 gaseous medium surrounding the wire. In a recent paper, 

 by Humphrey f , the effect of surrounding the inclinometer 

 wires by air, hydrogen, and carbon dioxide respectively was 

 studied. In this latter work, the relative dimensions of the 

 distance between the wires and of the chamber containing 

 them were such as to make it extremely improbable that the 

 main part of the heat transfer from the wires was effected by 

 convection. A comparison of the results obtained with those 

 previously referred to, in which the free convection effect 

 was of relatively greater importance, was on this account 

 impossible. The present paper, arising out of an investi- 

 gation into the distribution of velocities around a fine heated 

 platinum wire, details results showing how the mutual effect 

 experienced by two fine heated wires, surrounded by air at 

 atmospheric pressure, is conditioned by their distance apart, 

 and their disposition with regard to the walls of the 

 enclosure containing them. 



Experimental. 

 The apparatus employed is shown in elevation and sectional 



G-~ 



Fid I 



8 



Sectional Plan 



plan in fig. 1. The two fine platinum wires A, B, approxi- 

 mately O'l mm. in diameter, were soldered by means o( the 



* Proc. Roy. Soc. A. vol. xcvii. p. 276 (1920). 



t Proc. Phys. Soc. vol. xxxiii. Part iii. pp. L90-195 (1921). 



