While testing some ionization‐meters designed and constructed at the Department of Terrestrial Magnetism of the Carnegie Institution of Washington for use in a project proposed by Dr. ,V. F. Hess [see 1 of “References” at end of paper], it was found by K. L. Sherman that the rate of ion‐formation per cc in these meters was more than three times that measured under similar circumstances with Kolhörster penetrating‐radiation meter No. 5658 made by Günther and Tegetmeyer in 1928 (GT 5658). Perhaps the most convincing measure, of this contrast is provided by comparing the “Eve's numbers” (K), which were determined for the instruments.