Mr Kleeman, The Unstable Nature of the Ion in a Gas. 265 
in connexion with experiments on the nature of the ions in a 
discharge tube. It is found that hydrogen atoms and molecules 
positively charged are always present in the tube, and their 
apparent number may even be increased by the addition of a gas 
whose molecules do not contain hydrogen. At first sight this 
would seem to indicate that the nature of the positive ion is 
independent of the nature of the atom from which it is produced. 
But this explanation is not conclusive, since the increase in the 
number of hydrogen atoms can also be explained thermodynamic- 
ally. Hydrogen is always given off by the electrodes in the tube 
due to the discharge, and is therefore always initially present. 
Evidence was also obtained that a molecule when ionised 1s 
sometimes split into its constituent atoms. 
Fig. 1. 
Experiments on the Ionisation by Collision with Negative Ions. 
Further experiments were carried out along the same lines, 
especially with the negative ions, which will be described in this 
paper. For the experimental details (the same apparatus as before 
was used) the reader must consult the paper quoted. 
Fig. 2 shows two curves obtained with negative ions when 
ether vapour was in the chamber. The curve A was obtained 
with the ions drawn through the gauze from the space adjacent 
to its lower side. The curve B was obtained after placmg a 
quantity of radium near the chamber, in which case additional 
initial ions were made in the space between the gauze and plate 
by the y rays of the radium. These ions are not given an oppor- 
tunity of forming clusters. In the latter case the curve should 
be situated nearer to the zero than in the former, because in that 
ease we are dealing with a larger amount of initial ionisation. 
That this must be so will at once be seen on doubling all the 
ordinates of the curve A, which amounts to doubling the number 
