Experimental Fluctuations in the Ionization of Cosmic Ray Particles in a Thin Foil

On an exploratory basis, a cloud chamber has been controlled in its operation by a proportional counter mounted within it. As a selection device for events of high ionization this has been satisfactory, and information is given on the types of events actually observed. The ionization produced in the counter by single particles is shown to be subject to wide fluctuations. These are discussed with reference to existing theories on these theories are not wholly applicable to this case, as the foil represented by the gas is too thin. To these fluctuations is attributed to the large proportion of single particles seen in resultant pictures.