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L1V. The Velocity and Rate of Recombination of the Ions of 

 Gases exposed to Rontgen Radiation. By E. Rutherford, 

 M.A., JB.Sc, 1851 Exhibition Science Scholar, New Zealand 

 University, Trinity College, Cambridge* '. 



AIR which has been exposed to Rontgen radiation pre- 

 serves the power of discharging positive and negative 

 electrification a short time after the rays have ceased. It has 

 been shown (J. J. Thomson and McClelland, Proc. Roy. Soc. 

 lix. 1896) that a plate can be discharged some distance 

 from the direct line of radiation from the Crookes' tube by 

 blowing the Rontgenized air towards the plate, In this way 

 it is possible to discharge electrification after the air which 

 has been exposed to the rays has passed through a tube several 

 yards in length (J. J. Thomson and E. Rutherford, Phil. 

 Mag. Nov. 1896). 



In the following paper the duration of the q/ifer-conductivity 

 of air and other gases has been investigated, and from the 

 data thus obtained the velocity of the ions through various 

 gases has been determined. 



Two distinct methods of determining the duration of the 

 conductivity were used, both of which gave consistent results, 

 viz. : — 



(1) By blowing air at a known velocity along a tube, and 



testing the conductivity at different distances from 

 the point of action of the rays. 



(2) By applying an electromotive force to the gas at 



definite intervals after the rays have ceased, and 

 measuring the quantity of electricity that passed 

 through the gas. 

 In the first method an aluminium cylinder was connected 

 in series with a long brass tube 3 cm. in diameter and a metre 

 long. The aluminium cylinder was placed over an opening 

 in the metal tank in which the bulb and coil were placed in 

 order to completely screen off all external electrostatic 

 disturbances. All radiation to external points was carefully 

 screened off by a thick lead covering over the aluminium 

 cylinder. The aluminium tube was connected in series with 

 a gasometer filled with air, the pressure of which could be 

 regulated by weights placed on top. The air before reaching 

 the aluminium tube passed through a tube filled with glass 

 wool to remove the dust from the air. Three equal and 

 similar insulated electrodes were placed at known distances 



* Communicated by the Author. 



