Object Record

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Catalog Number 01.C.73
Object Name Electroscope
Title Electroscope to Measure Cosmic Rays
Artist Swann, William Francis Gray
Date ca. 1935
Description Insulated glass container with platinum wires, brass, and mesh.

Presented along with the papers of William Francis Gray Swann (APS Library).
Label Pioneering physicist William F. G. Swann used this instrument to study cosmic rays. Swann, the first director of the Bartol Research Foundation of the Franklin Institute, received a grant from the APS in 1935 to study nuclear atomic bursts produced by cosmic rays. Austrian physicist Victor Hess had first discovered these rays in 1912 when he carried an electrometer on a hot-air balloon flight. Hess noted that as he travelled farther away from the ground, radiation levels decreased. However, at some point the levels began to increase, indicating that radiation, or cosmic rays, were coming from space. In the 1930s, American physicists and organizations conducted cosmic-ray experiments with electroscopes in hot-air balloons. The February 1936 issue of Popular Mechanics magazine included an article on cosmic-ray studies, with a photograph of Dr. Swann holding the electroscope now in the APS collections. Scientists at the Bartol Research Foundation designed and constructed this instrument. Every time a cosmic ray struck the wire in the device, the charge was discharged and counted. Swann and other physicists also designed and installed other cosmic-ray devices, including telescopes to study the direction of cosmic radiation.
Dimension Details Too fragile to measure
Credit line American Philosophical Society. Gift at the bequest of William Francis Gray Swann, 1962.
Search Terms 20th century
twentieth century
measurement
scientific instrument
astronomy