16 



As a similar form of apparatus has been frequently em- 

 ployed where the introduction of a- gauze suggested a ready 

 means of localizing the field which was to be used for collect- 

 ing the ions which were blown along a tube — as, for example, 

 in the experiments of Townsend (8) upon diffusion of ions 

 and (9) in experiments upon the ions which are produced from 

 flames, etc. — it is of some additional interest to know what 

 effects may arise from the introduction o*f such a gauze. A 

 short account will therefore be given of some preliminary ex- 



Figs. 2 and 3. 



periments in which the size and nature of the gauze and the 

 distance between the central electrode and the gauze were 

 varied. 



The curv^es, fig. 2, show the results of experiments with a 

 brass gauze having 40 strands to the inch, two sets of wires 

 being interlaced at right angles to each other, each wire 



(8) Phil. Trans. Roy. Soc, cxcii., A 1900, pp. 129-158. 



(9) Langevin and Block, Comptes Rendus, cxxxix., 1904, p. 792. 



