Downey, Katherine Melvina2016-03-092016-03-091920-11https://hdl.handle.net/11299/178067University of Minnesota Ph.D. dissertation. November 1920. Major: Physics. Advisor: Professor W. F. G. Swann. 1 computer file (PDF); 17 pages. [421-437]. Reprinted in Physical Review.enPhysicsVariation with Pressure of the Residual Ionization Due to the Penetrating RadiationThesis or Dissertation