Wilson Marcy Powell (July 18, 1903 – March 2, 1974) was an American physicist and a member of the Physics department at the University of California, Berkeley. Biography The son of Harvard lawyer Wilson Marcy Powell Sr. and Elsie Knapp, Wilson was born in Litchfield, Connecticut. He matriculated into Harvard College in 1922 and graduated in 1926. During his undergraduate years, Powell went on two solar eclipse expeditions sponsored by Swarthmore College. He participated in his final eclipse expedition to the Arctic Circle nearly 50 years later. At the behest of his father, Powell entered Harvard Law School in 1926. However, he had always known that he wanted to do physics and was unable to focus on his law studies. His mother, Elsie persuaded her husband to allow their son to withdraw from the law school after a year and to begin graduate work in physics at Harvard. Powell completed a Ph.D. in Physics in 1933 under Theodore Lyman IV. Early career Powell worked as an assistant teacher at Harvard and Radcliffe from 1933 to 1935, and took on additional work at the Woods Hole Oceanographic Institute. He taught physics at Connecticut College from 1935 to 1937, and then Kenyon College in Ohio from 1937 to 1941. Research on cosmic rays In 1935, Powell became a research fellow at the Franklin Institute's Bartol Laboratory and began investigation of cosmic rays. During the Depression years, funds for research were difficult to secure. Powell managed to obtain financing for his research on cosmic rays and the construction of bigger and better cloud chambers from the Rumford Fund of the American Academy of Arts and Sciences, the Carnegie Institute, the Committee on Research of the American Philosophical Society and the Fund for Astrophysical Research. While at Bartol, Powell constructed two cloud chambers for cosmic ray study and developed a source of light at a much lower cost than the lighting used at the time. Awarded a Guggenheim Fellowship in 1941, Powell put together the Kenyon Cosmic Ray Expedition, and took a cloud chamber to the top of Mount Evans in Colorado. He was searching for a heavier-than-electron particle, known as the "mesotron." In a 17-foot-long trailer, a laboratory on wheels at a height of 14,125 feet, Powell and assistant Henry Meyer took about 12,000 photographs in order to capture a photo of the particle. He had made improvements to the cloud chamber, such