476 Dr. H. A, Wilson on the 



The same property may belong to impure platinum, and 

 the corresponding critical temperature may be even lower 

 than that of pure platinum. 



When the platinum is heated to the critical temperature in 

 question the gases begin to combine, and if the platinum is 

 heated still further, the rate of combination thereby set up in 

 the gases increases with the temperature of the metal. 



After heating the platinum sufficiently to start the reaction 

 of the gases, the reaction may be temporarily renewed by 

 raising the platinum to a temperature distinctly lower than 

 that which was required to start the reaction. 



The reaction between the gases is not produced by heating 

 them to a temperature at which they combine of themselves, 

 but is probably connected with the corpuscular discharge 

 which is known to be emitted by platinum. 



The experiments mentioned in this paper were carried out 

 in the laboratory of Professor Townsend, the Wykeham 

 Professor of Physics, to whom I wish to express my thanks. 



LV. The Electrical Conductivity of Flames. By Harold 

 A. Wilson, M.A., D.Sc, Fellow of Trinity College, 

 Cambridge, and Lecturer on Physics in King's College, 

 London *. 



(1) Flames containing no Salt Vapour. 



THE following paper contains an account of a series of 

 experiments on the conductivity of a coal-gas flame 

 for electricity between platinum electrodes immersed in the 

 flame f. In order to study the variation of the current with 

 the distance between the electrodes and the fall of potential 

 along the flame, a special burner was used to produce a long 

 narrow flame. The burner consisted of a fused quartz tube 

 25 cms. long and 2 cms. in diameter, having a single row of 

 holes each 1-5 mm. in diameter parallel to its axis. There 

 were 40 holes uniformly distributed into a row 20 cms. long. 

 One end of the tube was closed with an indiarubber stopper, 

 and the other was connected by means of an indiarubber 

 tube to a large Bunsen burner. The mixture of coal-gas and 

 air supplied by the Bunsen burner was burnt at the row of 

 holes, and formed a fairly uniform flame 20 cms. long and 

 about 4 cms. high. As electrodes two parallel disks of 

 platinum were used, each 1 cm. in diameter. One of these 



* Communicated by the Physical Society : read June 16, 1905. 



t An excellent account of the present state of our knowledge of this 

 subject by F. L. Tufts is contained in J. Stark's Jahrbuch der Radio- 

 aktivitdt und Mektronik, 1 Band, 1 Heft (1904). 



