[HENDERSON] DEPOSITS OF RADIUM, THORIUM AND ACTINIUM 167 
3. The rest-atoms were found to be initially all charged alike, 
either all positive or all neutral, when surrounded by molecules of a 
single kind. In air, hydrogen, oxygen, carbon dioxide, etc., the 
rest-atoms are initially all positively charged. In ether, water 
vapor. ethyl bromide, etc., the rest-atoms are initially all neutral. 
In atmospheres containing molecules of both types, the fraction of 
the rest-atoms positively charged depends on the relative munbers 
of the two kinds of gas molecules present. 
4, The recombination between rest-atoms and ions has been shown 
to consist of three distinct types, “volume,” “columnar” and “initial.” 
It has been pointed out that not only volume and columnar but also 
initial recombination should take place between ions themselves. 
5. A possible explanation of what takes place during recoil, has 
been advanced to account for the initial charged conditions of the 
rest-atoms in atmospheres composed of a single gas and of a mixture 
of two gases. 
I take this opportunity to express my gratitude to Prof. H. L. 
Bronson for his continual interest and advice throughout this investi- 
gation and without whose help this paper could not have been com- 
pleted. 
Sec. III, Sig. 3 
