This is one of three original electroscopes used by the Austrian scientist Victor Hess during his balloon ascensions to measure ionizing radiation in the atmosphere in the period from 1911 to 1913. This instrument is a version of a commercial model of a Wulff electroscope especially modified by its manufacturer, Günther & Tegetmeyer (mfr. number 4760), to take into account operating under reduced pressure at high altitudes. Data collected by Hess led him to the conclusion that the radiation was of extra-terrestrial origin. He was awarded the Nobel Prize in 1936 for this discovery of what came to be known as cosmic rays. Hess immigrated to the U.S. in 1938 where he became a professor at Fordham University. The electroscope was donated to NASM by Fordham in 1990.
