464 Mr. J. J. Lonsdale on the Ionization 



longitudinal motions of the bridge obtainable by striking or 

 plucking the A-string. Fig. 69, with a smaller motion o£ 

 the string excited by the plectrum, gives a larger motion 

 of the bridge. The last three figures (70-72) show the only 

 appreciable motions obtainable for this corner of the bridge 

 by exciting the E-string. Fig. 72 is very remarkable in 

 that the string's motion, though entirely vertical, leaves so 

 small a record, and yet the longitudinal motion of the other 

 corner of the bridge is quite considerable. 



Univ. Coll., Nottingham, 

 June 29th, 1910. 



XLVI. The Ionization produced by the Splashing of Mercury. 

 By J. J. Lonsdale, M.Sc.(Dunelm), B.Sc.(Lond.)*~ 



PREVIOUS work on the ionization produced by splash- 

 ing, or by bubbling gas through liquids has usually 

 been carried out with liquids having considerable vapour 

 pressure |. The results show that the ions produced generally 

 move with a very small velocity, varying from a few mms. 

 to *001 mm. per second under a potential gradient of one volt 

 per cm. The question is whether these small velocities are 

 due to the condensation of the vapours on the ions, or 

 whether, as Bloch J suggests, the ions are of a kind altogether 

 distinct from the usual Rontgen ray ions. With a view to 

 gaining evidence on this point, I have investigated the 

 ionization produced by splashing mercury, as there will be 

 little condensation in this case. As the mechanism of the 

 production of ions by the splashing process is not clear, various 

 other points have received attention. 



The apparatus used is shown in fig. 1. The splash- 

 chamber consisted of a wrought-iron cross-piece fitted with 

 nipples, allowing the splash-plate or the upper iron tube to 

 be readily removed. Mercury fell from the iron funnel A 

 on to the plate B, and the ions so produced were pulled by 

 an air current along two brass tubes, insulated from each 

 other and carrying two insulated electrodes, C and D, placed 

 axially in the tube. C and D could be connected when 

 desired to a Dolezalek electrometer. The connexions were, 

 of course, suitably screened by earthed conductors. With 

 ebonite insulation certain irregularities were shown when 

 the direction of the electric field was reversed in the space 



* Communicated by Dr. R. S. Willows. 



t Kiihler, Ann. der Physik, 1903, p. 1119. Aselmann, Ann. der 

 Physik, 1906, p. 960. 



X Bloch, Compte Rendus, cxh'. p. 54. 



